IllegalMonitorStateException in VertxBlockingOutput
**Describe the bug**

```
SEVERE [io.ver.cor.imp.ContextImpl] (vert.x-eventloop-thread-3) Unhandled exception: java.lang.IllegalMonitorStateException
        at java.base/java.lang.Object.notifyAll(Native Method)
        at io.quarkus.resteasy.runtime.standalone.VertxBlockingOutput$3.handle(VertxBlockingOutput.java:114)
        at io.quarkus.resteasy.runtime.standalone.VertxBlockingOutput$3.handle(VertxBlockingOutput.java:110)
        at io.vertx.core.http.impl.HttpServerResponseImpl.handleClosed(HttpServerResponseImpl.java:622)
        at io.vertx.core.http.impl.HttpServerResponseImpl.handleException(HttpServerResponseImpl.java:590)
        at io.vertx.core.http.impl.HttpServerRequestImpl.handleException(HttpServerRequestImpl.java:577)
        at io.vertx.core.http.impl.Http1xServerConnection.handleClosed(Http1xServerConnection.java:413)
        at io.vertx.core.net.impl.VertxHandler.lambda$channelInactive$4(VertxHandler.java:162)
```

**To Reproduce**
Can reproduce often if streaming a video via a Response.ok(File file) jaxrs request.

**Environment (please complete the following information):**
 - Quarkus version or git rev: 1.2.1.Final

diff --git a/extensions/resteasy/runtime/src/main/java/io/quarkus/resteasy/runtime/standalone/VertxBlockingOutput.java b/extensions/resteasy/runtime/src/main/java/io/quarkus/resteasy/runtime/standalone/VertxBlockingOutput.java
index fafae708f2f..e2775f5a0ce 100644
--- a/extensions/resteasy/runtime/src/main/java/io/quarkus/resteasy/runtime/standalone/VertxBlockingOutput.java
+++ b/extensions/resteasy/runtime/src/main/java/io/quarkus/resteasy/runtime/standalone/VertxBlockingOutput.java
@@ -9,6 +9,7 @@
 import io.vertx.core.Context;
 import io.vertx.core.Handler;
 import io.vertx.core.buffer.Buffer;
+import io.vertx.core.http.HttpConnection;
 import io.vertx.core.http.HttpServerRequest;
 
 public class VertxBlockingOutput implements VertxOutput {
@@ -111,7 +112,10 @@ private void awaitWriteable() throws IOException {
                     @Override
                     public void handle(Void event) {
                         if (waitingForDrain) {
-                            request.connection().notifyAll();
+                            HttpConnection connection = request.connection();
+                            synchronized (connection) {
+                                connection.notifyAll();
+                            }
                         }
                     }
                 };
['extensions/resteasy/runtime/src/main/java/io/quarkus/resteasy/runtime/standalone/VertxBlockingOutput.java']