Switch to moxstubout and mockpatch from oslotest

The fixtures in nova/openstack/common will be removed as
they have been removed from oslo-incubator. We should use
the fixtures from oslotest.

Note that oslotest uses mox3 instead of mox and some of the
tests were failing as a result which have been fixed in this
review. Only the failing tests have been fixed, so you will
see some tests use a mix of mock and mox3 as a result.

Based on feedback from Nova core, all existing references
to 'import mox' have been switched over to mox3 as well.

Change-Id: Ifa9dbb6f9bb1a358d815ae80cf928b65d5dcf5bd
Merge "Switch to moxstubout and mockpatch from oslotest"