Wait for the router port activation before deletion

The cleanup method ``_remove_router_interface_with_subnet_id`` should
wait for the router interface (port) activation before trying to delete
it. That will prevent a race condition between the deletion and the
port update.

Closes-Bug: #2083287
Change-Id: Id9029eb5a0558e74c62248fa08689aa1adee961a
1 file changed