db_clear should support subkeys

[Ihar Hrachyshka]

In OVN driver, when I need to clear one of fields inside e.g. 'external_ids' for Port_Group (or options, or other_config...), I don't have API in ovsdbapp to achieve it. I would like support for this added to db_clear function.

Also, support for subkeys in db_set may also need a revisit. I've tried this.

        ext_ids = pg['external_ids'].copy()
        ext_ids.pop(ovn_const.OVN_REV_NUM_EXT_ID_KEY)
        self.nb_api.db_set(
            'Port_Group', pg['name'],
            ('external_ids', ext_ids)).execute(check_error=True)

And it's not working too.

[Ihar Hrachyshka (ihar-hrachyshka)]

Here's a draft fix from Terry: https://paste.centos.org/view/ba69052e

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/ovsdbapp/+/879367

[OpenStack Infra (hudson-openstack)]

Change abandoned by "Terry Wilson <email address hidden>" on branch: master
Review: https://review.opendev.org/c/openstack/ovsdbapp/+/879367
Reason: db_remove is the proper way to do this