Comment 1 for bug 1843582

A proposal for how the systemd service files could look is proposed as part for the charm here: https://review.opendev.org/#/c/690025/

Note: the ``ovn_northd.service`` should probably be updated to pass in ``--ovn-manage-ovsdb=no`` instead of relying on the existence of ``/etc/openvswitch/ovn-northd-db-params.conf``. This works for the charm implementation as it will always write that file.