Comment 8 for bug 1737892

After a lot of debugging and checking logs from gates and from tests runs locally I found that problem comes when:

ovs agent will get "port_update" event (to set port as unbound) and port is already removed from br-int when it tries to get vif port in: https://github.com/openstack/neutron/blob/master/neutron/plugins/ml2/drivers/openvswitch/agent/ovs_neutron_agent.py#L1530 (port is removed because fullstack machine's destroy() method removes it just after call port_update() method.

In such case port is added to skipped_ports and is set as DOWN in neutron-db but ext_manager is not called then for such port so it will not clear stuff like bandwidth limit's QoS and queue records and also DSCP marking open flow rules for this port.