Wait for FIP status to get to DOWN in test_router_rescheduling

If we don't wait until the port actually gets to DOWN in database, we
may proceed to scheduling the router again and check floating IP status,
expecting it to be ACTIVE, but then catch DOWN still in database because
the router was slow to process the unscheduling event.

Closes-Bug: #1644937
Change-Id: I0806ead789953a4ff879ef9e6e77e1c66e658316
1 file changed