Add unit tests for cinder/api/versions

Added to the following unit tests:
  Test action args;
  Test get most recent update;
  Test create version entry;
  Test create feed.

Change-Id: I760e8f419be529cda969e848f151a8cab1053dce
Update upper bound of keystoneclient version.

This is the intermediate step so that we can update the the lower
bound of keystoneclient in openstack-requirements.

Change-Id: Ie6d973ccd1263243ebf0779ae59ef32416bf7087
Merge "Update upper bound of keystoneclient version."
Merge "Add unit tests for cinder/api/versions"