1150296 - Revises NoAvailableWorkers troubleshooting note for 2.5.1 changes

https://bugzilla.redhat.com/show_bug.cgi?id=1150296

The two-queues (black friday) rewrite changed this behavior in 2.5.1, so these docs really go with that change.
This is a good suggestion. I'm going to rework it before merging