[adam-collard, r=gnuoy] This branch prevents the swift-storage charm from thinking there was an OpenStack upgrade available at every config-changed.
I had to update the Amulet tests because they were incorrectly asserting that all of the swift services should have been restarted following a change to object-server-threads-per-disk. In fact, only the object services should be restarted, and only are (the test passed prior to this because of the bug in charm-helpers which caused the unconditional OpenStack upgrade, in turn restarting all of the services)