Turn ErrWorkflowClosing into a retryable error

[yycptt]

What changed?

• Turn ErrWorkflowClosing into a retryable error: resource exhausted with workflow busy cause.
• The error means workflow is about to close so the operation can not be applied at this time. But the operation will be able to be applied if workflow continues as new or get rejected if workflow completes. and by retrying, hopefully customer won't see the error (depending how fast they process their workflow task).

Why?

• so that user doesn't have to retry on their end in most cases.
• resource exhausted error also won't be retried by service handler.

How did you test it?

• Existing functional test

Potential risks

Is hotfix candidate?