Add keystoneclient and novaclient tests to tox
Add keystoneclient and novaclient tests to tox

We want to be able to test changes in requests-mock against some of our
consumers to ensure we don't break anyone.

Change-Id: I029c25d7274e0d7638d85cbf3dc6c42aad3a5463

stackforge/requests-mock,jamielennox/requests-mock