Ensure that LB VIF drivers creates the bridge if necessary

Fixes bug 1117770

In order for libvirt to use the bridge name the bridge must exist.

Change-Id: Ie24cfce8454e0c1bbfd9058787a1fd704790f03c
Changes GA code for tracking cross-domain.

Change-Id: I731d6b160588b59f01abe98699c144fdf4ae12ad
Merge "Changes GA code for tracking cross-domain."
Merge "Ensure that LB VIF drivers creates the bridge if necessary"