Get VIF_* constants from nova.network.model instead of neutron.extensions.portbindings
Get VIF_* constants from nova.network.model instead of neutron.extensions.portbindings

So that we no longer need to add any VIF_* constants to Neutron

beddari/calico,ocadotechnology/calico,nbartos/calico,neiljerram/felix,Metaswitch/calico,beddari/calico,alexhersh/calico,alexaltair/calico,neiljerram/felix,ocadotechnology/calico,anortef/calico,Metaswitch/calico,neiljerram/felix,kasisnu/calico,alexhersh/calico,alexaltair/calico,neiljerram/felix,TrimBiggs/calico,TrimBiggs/calico,nbartos/calico,fasaxc/felix,anortef/calico,kasisnu/calico,fasaxc/felix,matthewdupre/felix,matthewdupre/felix