Regression issue: Fast Jar not working using OpenShift and Docker strategy
## Describe the bug
When using the Docker strategy when deploying an application using OpenShift, the build failed because the generated artifacts are not found:

```
[INFO] [io.quarkus.container.image.openshift.deployment.OpenshiftProcessor] STEP 6: ENV JAVA_OPTIONS="-Dquarkus.http.host=0.0.0.0 -Djava.util.logging.manager=org.jboss.logmanager.LogManager"
[INFO] [io.quarkus.container.image.openshift.deployment.OpenshiftProcessor] --> 54085069869
[INFO] [io.quarkus.container.image.openshift.deployment.OpenshiftProcessor] STEP 7: COPY --chown=1001 target/quarkus-app/lib/ /deployments/lib/
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  01:09 min
[INFO] Finished at: 2021-03-30T09:47:32+02:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal io.quarkus:quarkus-maven-plugin:1.13.0.Final:build (default) on project openshift-quickstart-13: Failed to build quarkus application: io.quarkus.builder.BuildException: Build failure: Build failed due to errors
[ERROR] 	[error]: Build step io.quarkus.container.image.openshift.deployment.OpenshiftProcessor#openshiftBuildFromJar threw an exception: java.lang.IllegalStateException: Build:custom-1 failed! Dockerfile build strategy has failed.
[ERROR] 	at io.quarkus.container.image.openshift.deployment.OpenshiftProcessor.openshiftBuild(OpenshiftProcessor.java:444)
[ERROR] 	at io.quarkus.container.image.openshift.deployment.OpenshiftProcessor.lambda$openshiftBuild$10(OpenshiftProcessor.java:389)
[ERROR] 	at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183)
[ERROR] 	at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:195)
[ERROR] 	at java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:177)
[ERROR] 	at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1655)
[ERROR] 	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
[ERROR] 	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
[ERROR] 	at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150)
[ERROR] 	at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173)
[ERROR] 	at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
[ERROR] 	at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:497)
[ERROR] 	at io.quarkus.container.image.openshift.deployment.OpenshiftProcessor.openshiftBuild(OpenshiftProcessor.java:389)
[ERROR] 	at io.quarkus.container.image.openshift.deployment.OpenshiftProcessor.createContainerImage(OpenshiftProcessor.java:340)
[ERROR] 	at io.quarkus.container.image.openshift.deployment.OpenshiftProcessor.openshiftBuildFromJar(OpenshiftProcessor.java:257)
[ERROR] 	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[ERROR] 	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[ERROR] 	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[ERROR] 	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
[ERROR] 	at io.quarkus.deployment.ExtensionLoader$2.execute(ExtensionLoader.java:920)
[ERROR] 	at io.quarkus.builder.BuildContext.run(BuildContext.java:277)
[ERROR] 	at org.jboss.threads.EnhancedQueueExecutor$Task.run(EnhancedQueueExecutor.java:2415)
[ERROR] 	at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1452)
[ERROR] 	at java.base/java.lang.Thread.run(Thread.java:834)
[ERROR] 	at org.jboss.threads.JBossThread.run(JBossThread.java:501)
```

### Actual behavior
The build should find the artifacts in the right folder.

## To Reproduce

Steps to reproduce the behavior:
1. `mvn io.quarkus:quarkus-maven-plugin:999-SNAPSHOT:create     -DprojectGroupId=org.acme     -DprojectArtifactId=openshift-quickstart     -DclassName="org.acme.rest.GreetingResource"     -Dpath="/greeting"  -Dextensions=openshift`
2. cd `openshift-quickstart`
3. Deploy it using `mvn package -Dquarkus.kubernetes.deploy=true -Dquarkus.openshift.build-strategy=docker`

The maven command fails with the exception in the description.  

## Environment (please complete the following information):

### Quarkus version or git rev
999-SNAPSHOT or 1.13.0.Final
It worked fine using 1.11+

## Additional context
I think that this is a regression issue caused by the new fast jar method. If we change the target folder in the `Dockerfile.jvm` file from `target/quarkus-app` to `target`, then it starts working fine. (Not saying this is the right way to fix it).

diff --git a/extensions/container-image/container-image-openshift/deployment/src/main/java/io/quarkus/container/image/openshift/deployment/OpenshiftProcessor.java b/extensions/container-image/container-image-openshift/deployment/src/main/java/io/quarkus/container/image/openshift/deployment/OpenshiftProcessor.java
index ed0d451359b..b64ae4b9093 100644
--- a/extensions/container-image/container-image-openshift/deployment/src/main/java/io/quarkus/container/image/openshift/deployment/OpenshiftProcessor.java
+++ b/extensions/container-image/container-image-openshift/deployment/src/main/java/io/quarkus/container/image/openshift/deployment/OpenshiftProcessor.java
@@ -2,6 +2,7 @@
 
 import static io.quarkus.container.image.openshift.deployment.OpenshiftUtils.mergeConfig;
 import static io.quarkus.container.util.PathsUtil.findMainSourcesRoot;
+import static io.quarkus.deployment.pkg.steps.JarResultBuildStep.DEFAULT_FAST_JAR_DIRECTORY_NAME;
 
 import java.io.BufferedReader;
 import java.io.ByteArrayInputStream;
@@ -252,7 +253,8 @@ public void openshiftBuildFromJar(OpenshiftConfig openshiftConfig,
         //The contextRoot is where inside the tarball we will add the jars. A null value means everything will be added under '/' while "target" means everything will be added under '/target'.
         //For docker kind of builds where we use instructions like: `COPY target/*.jar /deployments` it using '/target' is a requirement.
         //For s2i kind of builds where jars are expected directly in the '/' we have to use null.
-        String contextRoot = config.buildStrategy == BuildStrategy.DOCKER ? "target" : null;
+        String outputDirName = out.getOutputDirectory().getFileName().toString();
+        String contextRoot = getContextRoot(outputDirName, packageConfig.isFastJar(), config.buildStrategy);
         if (packageConfig.isFastJar()) {
             createContainerImage(kubernetesClient, openshiftYml.get(), config, contextRoot, jar.getPath().getParent(),
                     jar.getPath().getParent());
@@ -266,6 +268,16 @@ public void openshiftBuildFromJar(OpenshiftConfig openshiftConfig,
         artifactResultProducer.produce(new ArtifactResultBuildItem(null, "jar-container", Collections.emptyMap()));
     }
 
+    private String getContextRoot(String outputDirName, boolean isFastJar, BuildStrategy buildStrategy) {
+        if (buildStrategy != BuildStrategy.DOCKER) {
+            return null;
+        }
+        if (!isFastJar) {
+            return outputDirName;
+        }
+        return outputDirName + "/" + DEFAULT_FAST_JAR_DIRECTORY_NAME;
+    }
+
     @BuildStep(onlyIf = { IsNormalNotRemoteDev.class, OpenshiftBuild.class, NativeBuild.class })
     public void openshiftBuildFromNative(OpenshiftConfig openshiftConfig, S2iConfig s2iConfig,
             ContainerImageConfig containerImageConfig,
['extensions/container-image/container-image-openshift/deployment/src/main/java/io/quarkus/container/image/openshift/deployment/OpenshiftProcessor.java']