MPLS OVS IPVPN driver, now requires OVS >= 2.5
MPLS OVS IPVPN driver, now requires OVS >= 2.5

Add an OVS version check to OVS MPLS IPVPN driver.

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