Comment 0 for bug 1896827

Currently, the port_update api in networking_ovn does not seem to
retain values in the external_ids that it may not care about.

That is not proper behavior as external ids in the lsp may be
storing data used by another entity in neutron, such as
ovn-octavia-provider.

Pseudo example:

1- create neutron port (which creates lsp in ovn)
2- add a new value to lsp's external_ids
3- invoke neutron: port_update
4- check an verify that after port update the key/value pair added in step 2 is still present

Ref code to networking-ovn port_update:

https://github.com/openstack/networking-ovn/blob/51e4351309c1f38c2ed353e6547c60ae9d5d50f5/networking_ovn/common/ovn_client.py#L456