Add some unit test plumbing

* Add a base test class derived from oslotest
* Remove py33 support from tox
* Cleanup pep8 errors

Also, Jenkins requires a test to exist to pass,
so this commit also contains a fix for Glance
client endpoint rotation and an associated
test case.

Change-Id: Id9cfbe6cf54c2d5b078cbcb6dcee690915afa7ba