Per [1], Nova expects the local OVSDB server to listen to TCP port 6640 on localhost. This patch adds the default var neutron_ovsdb_manager and creates a TCP listener on the OVN controller/compute, if needed. [1]: https://bugs.launchpad.net/charm-nova-compute/+bug/1852200 Change-Id: Id9573af6a0d533e74af6cd4cf9c32e4088fa5e79