I am trying to set an availability zone for OVN because skyline UI has a mandatory requirement to have an availability zone otherwise you are not allowed to create a network from skyline GUI. 

for OVN based deployment only option to set AZ is in ovn-cms-options

# ovs-vsctl set open_vswitch . external_ids:ovn-cms-options="enable-chassis-as-gw,availability-zones=az-0" 

Question: 

1. How do I configure in kolla-ansible to override or set ovn-cms-options on only gateway chassis? 

2. How does AZ work in OVN because OVN is anyway distributed as per documents, What if I just give foobar AZ name to meet Skyline requirement? Is it going to break anything?