Issue when using exit_handler with Kubeflow orchestrator
Environment:

Python 3.7.7
tfx==1.8.1
kfp==1.8.13
kfp-pipeline-spec==0.1.16
kfp-server-api==1.8.1

Issue description:


I have a tfx pipeline orchestrated by kubeflow pipeline. I upgraded tfx to version 1.8.1 in order to try to use the exit_handler support which was introduced in tfx 1.8.0.
I manage to build and compile my tfx pipeline in a kubeflow pipeline, but it looks like when we use the exit_handler, tfx orchestrator has a special behavior as we can see in `tfx/orchestration/kubeflow/utils.py`.

```python
# Key of dag for all TFX components when compiling pipeline with exit handler.
TFX_DAG_NAME = '_tfx_dag'
````

It seems like this result in an invalid argo workflow generated as when I try to use kfp API to create a run from the pipeline compiled file I get the following error from kubeflow API


```
Failed to create a new run.
(...)
"error_details":"Internal error: spec.templates[0].name: '_tfx_dag' is invalid: name must consist of alpha-numeric characters or '-', and must start with an alpha-numeric character (e.g. My-name1-2, 123-NAME)
(...)
```

Any idea if I am doing something wrong with how I use exit_handler ?

Do you think it is safe to update `TFX_DAG_NAME` to an argo complient name ?

Thank you for your time.



diff --git a/tfx/orchestration/kubeflow/utils.py b/tfx/orchestration/kubeflow/utils.py
index ef4631a3..b6f668df 100644
--- a/tfx/orchestration/kubeflow/utils.py
+++ b/tfx/orchestration/kubeflow/utils.py
@@ -18,7 +18,7 @@ from tfx.dsl.components.base import base_node
 from tfx.orchestration.kubeflow.decorators import FinalStatusStr
 
 # Key of dag for all TFX components when compiling pipeline with exit handler.
-TFX_DAG_NAME = '_tfx_dag'
+TFX_DAG_NAME = 'tfx-dag'
 
 
 def replace_exec_properties(component: base_node.BaseNode) -> None:
['tfx/orchestration/kubeflow/utils.py']