This patch adds
- setting nova config param 'force_config_meta' to True
as metadata service is not supported by OVN yet.
- Add the necessary iptables rules to allow ovsdb-server
traffic for Northbound and Southboud databases.
- Update the release notes for OVN.
Change-Id: If1a2d07d66e493781b74aab2fc9b76a6d58f3842
Closes-bug: #1670562