Fixes bug 867456 adds reprocessing queue to rabbitmq config

This adds a 'reprocessing' queue to the mix of queues we have available. 

I am putting this out there for discussion: 

* Is it ok to have the reprocessing and standard queues "round robin"? 
* The priority queue still gets checked every other time through the loop this way, rather than every third time. Is that too often?  The magic is in `crashstorage.py`

There's probably a better way to do this. Open to suggestions. :)

Writing tests for this was hard.