Description of problem:

When setting up their new RHOSP 16.2.4 cluster one of my partners got the warning:
"WARNING: Following parameter(s) are defined but not currently used in the deployment plan. These parameters may be valid but not in use due to the service or deployment configuration. CinderEnableNetappBackend, CtlplaneNetworkAttributes, ..."

The parameter seems to be set in the file builddir/tripleo-config-generated-env-files/undercloud_parameters.yaml.                                                                              

They also do have a second, but older cluster running 16.2 where this parameter is not present in the created files.

I've already checked the source of the triple-o client and the heat templates, also I have compared the two installation templates regarding the undercloud conf (please see case 03450021) but I'm not sure which config directive would set/not-set this parameter.

An upstream bug was already created to track upstream:

We never set [Networks, net_attributes_map, ctlplane] in Train. The PingTestGatewayIPsMap tries to use that information but it will always result in 'null' since the data is never set in net_attributes_map.

There is a missing backport: https://review.opendev.org/c/openstack/tripleo-heat-templates/+/753282

The PingTestGatewayIPsMap[1] which is the fix for RHBZ#1875962 tries to get the ctlplane gateways.

overcloud.j2.yaml#L1111
 {get_attr: [Networks, net_attributes_map, ctlplane, subnets, {get_param: {{role.name}}ControlPlaneSubnet}, gateway_ip]}

However, we never set anything for the ctlplane in Train so that would return "null" which does not create an error since null is filtered in the YAQL on overcloud.j2.yaml#L1109.

[1] https://opendev.org/openstack/tripleo-heat-templates/src/branch/stable/train/overcloud.j2.yaml#L1105-L1111