1124570 - Adds two-queue implementation for reserved resources

https://bugzilla.redhat.com/show_bug.cgi?id=1124570

This BZ implements this [design and TODO list](https://fedorahosted.org/pulp/wiki/TwoQueueReservedResourceDesign). Refer to that doc for more info on what is contained in this PR.
I adjusted this test to only have the unique query return one worker and assert that delete is called on it. The fact that a list is returned for a query that can only return one thing is a problem with the code, but shouldn't be reflected in the test. Thanks for pointing out