Ensure test_cleanup_stale_devices fails gracefully
Ensure test_cleanup_stale_devices fails gracefully

Give some time for devices to be cleared before we claim defeat.

Change-Id: I34b2ec634f1c9ec27a1b82cc3f55a5e0b7d71237
Closes-bug: #1604115

igor-toga/local-snat,igor-toga/local-snat,openstack/neutron,eayunstack/neutron,cloudbase/neutron,huntxu/neutron,mahak/neutron,mahak/neutron,openstack/neutron,noironetworks/neutron,eayunstack/neutron,mahak/neutron,noironetworks/neutron,huntxu/neutron,cloudbase/neutron,sebrandon1/neutron,openstack/neutron,sebrandon1/neutron