No wonder I couldn't figure out (again) how the Nova vif driver was
figuring out which physical OVS bridge to plug a Capnet VM NIC into...
I had forgotten about this little guy. This is a simple wrapper for
the Nova network API Neutron driver that adds a couple of
Capnet-specific fields into the VIF info. This seemed to be the way
to do it at the time... maybe there's a way to not have to do it