User cannot know the result when webhook response and backend work are split

[yk634]

What happened: The implementation associated with the issue(https://github.com/screwdriver-cd/screwdriver/issues/1769) allows for a split between backend work and webhook response.

If this feature is used, the user will not know the result of the backend work such as 4XX error or "No jobs to start". 200 is returned as the status code upon successful enqueue of the webhook information.

This is information that can be found in the SCM's hook status if this feature is not used.

What you expected to happen: Even when splitting the webhook reponse and the backend work, the user can know the result of the backend work

[jithine]

is that important ? for no jobs to start, we should probably look at alternatives to let users know a webhook activity didn't start an event