The subnet field in metdadata port is incorrectly updated in some cases

[Dong Jun]

After the following steps, the subnet field in the metdadata port is incorrectly updated, it will contain all subnets regardless of the subnet supports dhcp or not.

1st: Create two subnets in same network, one with enable_dhcp=True and the other with enable_dhcp=False.[1]
2nd: Update the first subnet, e.g. updating subnet name
   openstack subnet set --name subnet2-new 639659e1-d11e-445e-8fc0-3f946e71daee

Then metadata port contains both of the two subnets, that's incorrect.[2]

Seems there are two issues, one is enable_dhcp=[1] is missing in filter and the other is we did not clear the subnets which are disabled.

Issue 1: https://github.com/openstack/networking-ovn/blob/2ccd34397683c0deab4a76d9eba2d61cc8187da8/networking_ovn/common/ovn_client.py#L1158
Issue 2: https://github.com/openstack/networking-ovn/blob/2ccd34397683c0deab4a76d9eba2d61cc8187da8/networking_ovn/common/ovn_client.py#L1169

[1]
ovn lsp column:
56c514b1-427d-45a3-b4e1-35fb322396a4 ["fa:16:3e:ad:04:00 10.0.0.66"] [] [] [] true {"neutron:cidrs"="10.0.0.66/26", "neutron:device_id"="", "neutron:port_name"="", "neutron:project_id"="0134078dd4e54009bc64cac8dc0fa733"} "790b1d9c-4926-4a95-9451-528f17d5c1da" {requested-chassis=""}

stack@c3:~/networking-ovn$ openstack subnet show 639659e1-d11e-445e-8fc0-3f946e71daee
+-------------------------+--------------------------------------+
| Field | Value |
+-------------------------+--------------------------------------+
| cidr | 10.0.0.64/26 |
| enable_dhcp | True |
| gateway_ip | 10.0.0.65 |
| network_id | 69e1e4d1-5576-4cbf-8f01-8873122c5600 |
| project_id | 0134078dd4e54009bc64cac8dc0fa733 |
...
+-------------------------+--------------------------------------+

stack@c3:~/networking-ovn$ openstack subnet show e31f1af1-0e88-4194-bd58-81d5b5a6cba2
+-------------------------+--------------------------------------+
| Field | Value |
+-------------------------+--------------------------------------+
| cidr | 10.0.0.192/26 |
| enable_dhcp | False |
| gateway_ip | 10.0.0.193 |
| network_id | 69e1e4d1-5576-4cbf-8f01-8873122c5600 |
...
+-------------------------+--------------------------------------+

stack@c3:~/networking-ovn$ openstack port show 790b1d9c-4926-4a95-9451-528f17d5c1da
+-----------------------+--------------------------------------------------------------------------+
| Field | Value |
+-----------------------+--------------------------------------------------------------------------+
| device_owner | network:dhcp |
| fixed_ips | ip_address='10.0.0.66', subnet_id='639659e1-d11e-445e-8fc0-3f946e71daee' |
| id | 790b1d9c-4926-4a95-9451-528f17d5c1da |
| network_id | 69e1e4d1-5576-4cbf-8f01-8873122c5600 |
...
+-----------------------+--------------------------------------------------------------------------+

[2]
stack@c3:~/networking-ovn$ openstack port show 790b1d9c-4926-4a95-9451-528f17d5c1da
+-----------------------+---------------------------------------------------------------------------+
| Field | Value |
+-----------------------+---------------------------------------------------------------------------+
| admin_state_up | UP |
| device_owner | network:dhcp |
| fixed_ips | ip_address='10.0.0.194', subnet_id='e31f1af1-0e88-4194-bd58-81d5b5a6cba2' |
| | ip_address='10.0.0.66', subnet_id='639659e1-d11e-445e-8fc0-3f946e71daee' |
| id | 790b1d9c-4926-4a95-9451-528f17d5c1da |
| network_id | 69e1e4d1-5576-4cbf-8f01-8873122c5600 |
...
+-----------------------+---------------------------------------------------------------------------+