tempest: Skip QoS test until fixed
tempest: Skip QoS test until fixed

The test is failing intermittently. In order to reach a better stability
of the job running in-tree tempest tests, this patch skips the test
until we come up with a proper fix.

Change-Id: I37f1488db258f6a4d383fb472cb5433c65371ac5
Related-bug: 1662109

openstack/neutron,mahak/neutron,mahak/neutron,huntxu/neutron,eayunstack/neutron,huntxu/neutron,noironetworks/neutron,mahak/neutron,openstack/neutron,openstack/neutron,eayunstack/neutron,noironetworks/neutron