libvirt vif-plugging fixes.  Fixes bug 939252 , bug 939254
libvirt vif-plugging fixes.  Fixes bug 939252 , bug 939254

- fix OVS vif-plugging on red hat / fedora by supporting recent libvirt
change that provides OVS + libvirt integration.
- Create unit tests that provide coverage for all libvirt vif drivers
- Correctly set vm-uuid flag in existing OVS vif-plugging mechanism.

Change-Id: I29eeeda92d44a1c026d1c17cf169a1bf2b5a0cc1

n0ano/ganttclient