Remove explicit adding QoS policy  to the cleianup

The _create_qos_policy method mistakenly added the policy object
to the cleanup, whereas delete_qos_policy expects a policy_id

But in next steps qos_policy is correctly deleted by
BaseNetworkTest.cleanup_resources

Change-Id: If35d7e5dd14a508085dde4e719f6f1e4386d8e66
1 file changed