Bug 2069580

+++ This bug was initially created as a clone of Bug #2063978 +++

An OVN provider Load Balancer allows the creation of members without specifying the subnet-id. The internal logic allows OVN provider to create the member by associating it with the subnet-id of the pool to which it belongs, but the member is stored in Octavia DB without a reference to the subnet_id associated with the pool.

Subsequently, when an attempt is made to delete a member that was created without specifying the subnet_id to which it belongs, it is left in an ERROR state, while a member that did include that parameter at creation time is deleted correctly.

Steps to Reproduce:
1. Create a load balancer with OVN as provider
2. Create a listener and a pool associated to LB create in 1.
3. Create a member without parameter subnet-id

stack@ubuntu2004:~/devstack$ openstack loadbalancer member create --name vm1 --address $IPVM01 --protocol-port 80 pool1
+---------------------+--------------------------------------+
| Field               | Value                                |
+---------------------+--------------------------------------+
| address             | 192.168.100.136                      |
| admin_state_up      | True                                 |
| created_at          | 2022-03-14T17:12:10                  |
| id                  | c8245713-ef5f-4278-8c03-b39d5cf7fbf0 |
| name                | vm1                                  |
| operating_status    | NO_MONITOR                           |
| project_id          | edcc48bd917e4d668ab6b9b892a40cb5     |
| protocol_port       | 80                                   |
| provisioning_status | PENDING_CREATE                       |
| subnet_id           | None                                 |
| updated_at          | None                                 |
| weight              | 1                                    |
| monitor_port        | None                                 |
| monitor_address     | None                                 |
| backup              | False                                |
| tags                |                                      |
+---------------------+--------------------------------------+

4. Try to delete the member created in 3.

stack@ubuntu2004:~/devstack$ openstack loadbalancer member delete pool1 vm1
stack@ubuntu2004:~/devstack$ openstack loadbalancer member list pool1
+--------------------------------------+------+----------------------------------+---------------------+-----------------+---------------+------------------+--------+
| id                                   | name | project_id                       | provisioning_status | address         | protocol_port | operating_status | weight |
+--------------------------------------+------+----------------------------------+---------------------+-----------------+---------------+------------------+--------+
| c8245713-ef5f-4278-8c03-b39d5cf7fbf0 | vm1  | edcc48bd917e4d668ab6b9b892a40cb5 | ERROR               | 192.168.100.136 |            80 | NO_MONITOR       |      1 |
+--------------------------------------+------+----------------------------------+---------------------+-----------------+---------------+------------------+--------+


Expected result:
Member is deleted correctly

Actual result:
Member keeps in ERROR state.