CN do not clear QoS rules when ovs-agent restart

[Chengqian Liu]

I runned a test about qos(driver=openvswitch) based rocky and found the following problems.

1. craete a vm and found its port ,eg port_id= PORT_ID_A .
2. create a policy(eg , id=POLICY_ID) and create bandwidth_limit_rule (max_kbps=50000).
3. update port PORT_ID_A with qos_policy POLICY_ID.
4. 'ovs-vsctl list interface PORT_ID_A' to ensure its correct.

Everything was working fine, so we continue

5. stop neutron-openvswitch-agent
6. delete bandwidth_limit_rule in qos_policy POLICY_ID.
7. 'ovs-vsctl list interface PORT_ID_A' again ,
   I found 'ingress_policing_rate' and 'ingress_policing_burst' were not changed.
   That was not what I wanted.