Make sure workflow_task_execution_failed always has a failure_reason

[Quinn-With-Two-Ns]

closes #2418

[cretz]

This was a bit confusing to follow with handle, but since it's just adding a tag to existing metric, LGTM. I am now curious the situation this code is called in because I am afraid it actually won't return a task failure to the server.

[Quinn-With-Two-Ns]

I am now curious the situation this code is called in because I am afraid it actually won't return a task failure to the server.

Yes that is correct, we don't report a task to the server if we are retrying a task multiple times to control the task retry behaviour