Description of problem:
OSP17 environment with OVN+SRIOV configured

sriov_agent.ini includes the following minimum BW configuration that should be reported to placement:
[sriov_nic]                                                                                                                                                                                                                                   
physical_device_mappings=datacentre:enp7s0f3,datacentre:enp5s0f0
resource_provider_bandwidths=enp7s0f3:10000000:10000000,enp5s0f0:10000000:10000000
resource_provider_hypervisors=enp7s0f3:computesriov-0.localdomain,enp5s0f0:computesriov-0.localdomain                                                                                                                                         

placement section is correctly configured on neutron.conf:
[placement]
auth_url=http://10.20.1.65:5000
username=nova
password=D6BO88QBbKbEYI76XkNzX5W68
project_domain_name=Default
project_name=service
user_domain_name=Default
region_name=regionOne
auth_type=password


When the sriov-agent running in a compute node is restarted, it successfully generates the information that should be reported to placement:
2022-07-01 08:03:13.803 526516 INFO neutron.plugins.ml2.drivers.mech_sriov.agent.sriov_nic_agent [-] Physical Devices mappings: {'datacentre': ['enp7s0f3', 'enp5s0f0']}
2022-07-01 08:03:13.804 526516 INFO neutron.plugins.ml2.drivers.mech_sriov.agent.sriov_nic_agent [-] Exclude Devices: {}
2022-07-01 08:03:13.804 526516 INFO neutron.plugins.ml2.drivers.mech_sriov.agent.sriov_nic_agent [-] Resource provider bandwidths: {'enp7s0f3': {'egress': 10000000, 'ingress': 10000000}, 'enp5s0f0': {'egress': 10000000, 'ingress': 1000000
0}}
2022-07-01 08:03:13.804 526516 INFO neutron.plugins.ml2.drivers.mech_sriov.agent.sriov_nic_agent [-] Resource provider inventory defaults: {'allocation_ratio': 1.0, 'min_unit': 1, 'step_size': 1, 'reserved': 0}
2022-07-01 08:03:13.804 526516 INFO neutron.plugins.ml2.drivers.mech_sriov.agent.sriov_nic_agent [-] Resource provider hypervisors: {'enp7s0f3': 'computesriov-0.localdomain', 'enp5s0f0': 'computesriov-0.localdomain'}
2022-07-01 08:03:13.805 526516 DEBUG neutron.plugins.ml2.drivers.mech_sriov.agent.eswitch_manager [-] Number of VFs configured on device enp7s0f3: 5 get_numvfs /usr/lib/python3.9/site-packages/neutron/plugins/ml2/drivers/mech_sriov/agent/
eswitch_manager.py:133
2022-07-01 08:03:13.805 526516 DEBUG neutron.plugins.ml2.drivers.mech_sriov.agent.eswitch_manager [-] Number of VFs configured on device enp5s0f0: 5 get_numvfs /usr/lib/python3.9/site-packages/neutron/plugins/ml2/drivers/mech_sriov/agent/
eswitch_manager.py:133


However, the neutron server is unable to send those data to placement:
2022-07-01 08:03:13.967 20 ERROR neutron_lib.callbacks.manager [req-f40ac07f-9e01-480d-b4a3-11cd63ade5f1 - - - - -] Error during notification for neutron.services.placement_report.plugin.PlacementReportPlugin.handle_placement_config-1384518 agent, after_update: AttributeError: 'OVNMechanismDriver' object has no attribute 'agent_type'
2022-07-01 08:03:13.967 20 ERROR neutron_lib.callbacks.manager Traceback (most recent call last):
2022-07-01 08:03:13.967 20 ERROR neutron_lib.callbacks.manager   File "/usr/lib/python3.9/site-packages/neutron_lib/callbacks/manager.py", line 197, in _notify_loop
2022-07-01 08:03:13.967 20 ERROR neutron_lib.callbacks.manager     callback(resource, event, trigger, **kwargs)
2022-07-01 08:03:13.967 20 ERROR neutron_lib.callbacks.manager   File "/usr/lib/python3.9/site-packages/neutron/services/placement_report/plugin.py", line 204, in handle_placement_config
2022-07-01 08:03:13.967 20 ERROR neutron_lib.callbacks.manager     if agent['agent_type'] not in self._agents.supported_agent_types:
2022-07-01 08:03:13.967 20 ERROR neutron_lib.callbacks.manager   File "/usr/lib/python3.9/site-packages/neutron/services/placement_report/plugin.py", line 264, in supported_agent_types
2022-07-01 08:03:13.967 20 ERROR neutron_lib.callbacks.manager     self._supported_agent_types = [
2022-07-01 08:03:13.967 20 ERROR neutron_lib.callbacks.manager   File "/usr/lib/python3.9/site-packages/neutron/services/placement_report/plugin.py", line 265, in <listcomp>
2022-07-01 08:03:13.967 20 ERROR neutron_lib.callbacks.manager     driver.obj.agent_type
2022-07-01 08:03:13.967 20 ERROR neutron_lib.callbacks.manager AttributeError: 'OVNMechanismDriver' object has no attribute 'agent_type'



This didn't fail in OSP16.2, so this bug is a regression.



Version-Release number of selected component (if applicable):
RHOS-17.0-RHEL-9-20220628.n.1

How reproducible:
100%

Steps to Reproduce:
1. use the configuration described above, restart an sriov agent and check the neutron server logs
2. alternatively, run this downstream job: https://rhos-ci-jenkins.lab.eng.tlv2.redhat.com/job/DFG-network-networking-ovn-17.0_director-rhel-virthost-3cont_2comp-ipv4-vlan-sriov/
3.

Actual results:
$ openstack --os-placement-api-version 1.17  resource provider list
+--------------------------------------+----------------------------+------------+--------------------------------------+----------------------+
| uuid                                 | name                       | generation | root_provider_uuid                   | parent_provider_uuid |
+--------------------------------------+----------------------------+------------+--------------------------------------+----------------------+
| 01db300f-19f4-4f44-828c-30fdbb844f34 | computesriov-1.localdomain |        326 | 01db300f-19f4-4f44-828c-30fdbb844f34 | None                 |
| 5ddc8a22-2a81-47b0-b5b4-d742de6dd6fa | computesriov-0.localdomain |        351 | 5ddc8a22-2a81-47b0-b5b4-d742de6dd6fa | None                 |
+--------------------------------------+----------------------------+------------+--------------------------------------+----------------------+


Expected results:
Something like this is expected (see documentation at https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/16.2/html-single/networking_guide/index#guaranteed-min-bw_config-qos-policies)
$ openstack --os-placement-api-version 1.17  resource provider list
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| uuid                                 | name                                                | generation | root_provider_uuid                   | parent_provider_uuid                 |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| 31d3d88b-bc3a-41cd-9dc0-fda54028a882 | dell-r730-014.localdomain                           |         28 | 31d3d88b-bc3a-41cd-9dc0-fda54028a882 | None                                 |
| 6b15ddce-13cf-4c85-a58f-baec5b57ab52 | dell-r730-063.localdomain                           |         18 | 6b15ddce-13cf-4c85-a58f-baec5b57ab52 | None                                 |
| e2f5082a-c965-55db-acb3-8daf9857c721 | dell-r730-063.localdomain:NIC Switch agent          |          0 | 6b15ddce-13cf-4c85-a58f-baec5b57ab52 | 6b15ddce-13cf-4c85-a58f-baec5b57ab52 |
| d2fb0ef4-2f45-53a8-88be-113b3e64ba1b | dell-r730-014.localdomain:NIC Switch agent          |          0 | 31d3d88b-bc3a-41cd-9dc0-fda54028a882 | 31d3d88b-bc3a-41cd-9dc0-fda54028a882 |
| f1ca35e2-47ad-53a0-9058-390ade93b73e | dell-r730-063.localdomain:NIC Switch agent:enp6s0f1 |         13 | 6b15ddce-13cf-4c85-a58f-baec5b57ab52 | e2f5082a-c965-55db-acb3-8daf9857c721 |
| e518d381-d590-5767-8f34-c20def34b252 | dell-r730-014.localdomain:NIC Switch agent:enp6s0f1 |         19 | 31d3d88b-bc3a-41cd-9dc0-fda54028a882 | d2fb0ef4-2f45-53a8-88be-113b3e64ba1b |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------