Comment 6 for bug 1607714

The device detach from the guest in libvirt is asynchronous, so this must be much slower in libvirt 1.3.1 on xenial nodes, so neutron is telling us that the port is detach (device_id is None on the port) after detach - which is what the tempest test is polling on - before the interface is actually detached from the guest.

So we probably need a retry loop in detach_interface in the libvirt driver (like we have for detach_volume) to retry until timeout for the interface to be gone from the guest and consider the detach successful.