Cleans up test data from limit tests

Change-Id: Ibd10e800b3108bfbb5bce076d3c1566cac3eb138
Cleanup fixture data added to test instances

Change-Id: I1c8f603dc520f2483630a902a4f93fd5f04b05b4
Cleanup keystoneclient tests

I remove redundant calls to load backends and initialize the database to
hopefully make these tests a little faster. I also added some cleanup
for instance attributes to help with memory consumption.

Change-Id: If2afec11266e0cd4cd132800259c4d4f84644600
Merge "Cleans up test data from limit tests"
Merge "Cleanup fixture data added to test instances"
Merge "Cleanup keystoneclient tests"