Every reactive charm that uses charms.openstack and implements unit
testing needs to mock charmhelpers, as otherwise the tests blow up.
This patch uses the mocking of charmhelpers in charms.openstack so that
a charm layer can just import test_mocks and charmhelpers will be mocked
out along with setting up a default
charmhelpers.c.o.u.OPENSTACK_RELEASES so that when an OpenStackCharm()
derived charm class won't fail on definition.
Change-Id: Id6537afcd24840a008a537543a15cfe5fd278886
Related-Bug: #1693017
Depends-On: I5ac40617ee30e5f421ec16fc7592177a5e6aa166
1890f3ce55