Add device_owner to gateway port search criteria

When veryfing a gateway, search only for those ports
in the router which are tagged with proper device_owner
attribute.

The change addresses a case when networking-opencontrail
needs more ports with the same device_id and network_id
for any created router. This is needed for compatibility
with TungstenFabric.

Change-Id: If1c711547542460ebb3f3f9371a09669edb6ce5d
1 file changed