Comment 1 for bug 1922168

Proposed fix:
https://review.opendev.org/c/openstack/tripleo-heat-templates/+/783222

This worked for me:

1. Apply the patch to THT
2. On a Compute node:
ovs-vsctl set open . external_ids:ovn-cms-options=enable-chassis-as-gw
3. Add env file:
~~~
parameter_defaults:
  OVNCMSOptions: ""
~~~
4. Re-run deployment with included env file:

Before:
{hostname=overcloud-novacompute-0.bne-home.net, ovn-bridge=br-int, ovn-bridge-mappings="datacentre:br-ex", ovn-cms-options=enable-chassis-as-gw, ovn-encap-ip="172.16.0.39", ovn-encap-type=geneve, ovn-match-northd-version="true", ovn-openflow-probe-interval="60", ovn-remote="tcp:172.16.2.207:6642", ovn-remote-probe-interval="60000", rundir="/var/run/openvswitch", system-id="4b01dab1-8778-42c5-93fa-1e9dffe2f0de"}

After:
[root@overcloud-novacompute-0 ~]# ovs-vsctl get open . external_ids
{hostname=overcloud-novacompute-0.bne-home.net, ovn-bridge=br-int, ovn-bridge-mappings="datacentre:br-ex", ovn-encap-ip="172.16.0.39", ovn-encap-type=geneve, ovn-match-northd-version="true", ovn-openflow-probe-interval="60", ovn-remote="tcp:172.16.2.207:6642", ovn-remote-probe-interval="60000", rundir="/var/run/openvswitch", system-id="4b01dab1-8778-42c5-93fa-1e9dffe2f0de"}