reader: not exiting backoff

In the case where you backoff, test with RDY 1, and then requeue the message with backoff=False, you don't ever retry another message and exit backoff state.
Since we moved to triggers here, we need to specify intent absent that state. I'm failing at naming for that task. 

I'm inclined to leave this as a simpler `when in backoff each message you process either causes you to backoff more, or return closer to normal processing` and just remove the old 3rd state (in backoff, but a neither success or failure in processing a message that does not change backoff state).