Split up metering test case into plugin + test case

Currently the metering test case includes setUp code as well
as the tests themselves. Splitting up the test case class
into two allows other test cases to inherit the metering
plugin class without inherting (And implicitly re-running)
the tests themselves.

Closes-Bug: #1336198
Change-Id: I4427fcd17cc3d28189f9f74df487084cf35c1634
Make readme reference git.openstack.org not github

Point to our offical mirror instead of github.

Change-Id: I43c3d5ce4f92f35ed4fe5bddce5a5d19016ab988
Merge "Make readme reference git.openstack.org not github"
Merge "Split up metering test case into plugin + test case"