IPVPN MPLS OVS driver: fix an interface initialization issue
IPVPN MPLS OVS driver: fix an interface initialization issue

fixes a regression in a1ceb53d in the case where GRE is not used

openstack/networking-bagpipe-l2,openstack/networking-bagpipe,stackforge/networking-bagpipe-l2,openstack/networking-bagpipe,openstack/networking-bagpipe-l2,stackforge/networking-bagpipe-l2