ovn-controller-vtep: occasional failure in "binding 1" test case

ovn-controller-vtep: occasional failure in "binding 1" test case

The ovn-controller-vtep "binding 1" test case fails occasionally
due to a race with the ovs-vtep daemon.  If ovs-vtep happens to
execute handle_physical() after "ovs-vsctl del-port p0", but before
the test script has executed "vtep-ctl del-port br-vtep p0", the
latter command will fail because ovs-vtep will have already deleted
p0 from the vtep db.

Eliminate this race while adding an additional check to verify that
ovs-vtep is working as expected by waiting for ovs-vtep to remove
entries for the deleted physical ports from the vtep db.

Signed-off-by: Lance Richardson <lrichard@redhat.com>
Suggested-by: Darrell Ball <dlu998@gmail.com>
Acked-by: Darrell Ball <dlu998@gmail.com>
Signed-off-by: Russell Bryant <russell@ovn.org>