Fix the testing template when there aren't any testing updates
Fix the testing template again

The previous commit fixed the case where we had no updates in testing.

Unfortunately, I just realised that it broke the case where we do have
some updates in testing.

This now fixes both cases.
Move sort_updates into bodhi.util, and write a unit test for it.
Sort the updates right before tagging
Reverse our sorted updates so we tag the highest nvr last.
Test the last sorted update as well
Temporarily disable fedmsg in the masher code paths. (github#115)