Remove mox in test_virt_drivers.py
Remove mox in test_virt_drivers.py

Replace stubs.Set with stub_out or mock in
nova/tests/unit/virt/test_virt_drivers.py.

Change-Id: I3af68f745ffb23ef2b5407ccec0bebf4b2645734
Implements: blueprint mox-removal

klmitch/nova,openstack/nova,mikalstill/nova,phenoxim/nova,mikalstill/nova,openstack/nova,mahak/nova,gooddata/openstack-nova,openstack/nova,klmitch/nova,gooddata/openstack-nova,mahak/nova,phenoxim/nova,mikalstill/nova,rahulunair/nova,rahulunair/nova,gooddata/openstack-nova,klmitch/nova,klmitch/nova,mahak/nova,gooddata/openstack-nova,rahulunair/nova