Add ctlplane network attrs to Networks resource output

Add the attributes of ctlplane network and subnets to
the output of the Networks resource.

Also, set 'ctlplane_mtu' in group_vars. Follow-up changes
will add other ctlplane subnet attributes to group_vars.

The ctlplane attributes are added to the plan environment
by the depends-on tripleoclient change.

Depends-On: https://review.opendev.org/753195
Change-Id: Ic1772b384ad5b2003563b4e3d41a4a2f0e82f8e6

network/networks.j2.yaml

@@ -6,6 +6,13 @@ parameters:
   CtlplaneNetworkCidrs:
     type: json
     description: Cidrs for the ctlplane network.
+  CtlplaneNetworkAttributes:
+    type: json
+    default: {}
+    description: >
+      A map containing attributes of the undercloud ctlplane network and
+      subnets. NOTE: The value for this parameter is automatically populated in
+      the plan environment by tripleoclient.
 
 resources:
   {%- for network in networks if network.enabled|default(true) %}
@@ -20,7 +27,6 @@ resources:
   NetworkExtraConfig:
     type: OS::TripleO::Network::ExtraConfig
 
-
 outputs:
   net_cidr_map:
     value:
@@ -43,6 +49,7 @@ outputs:
       {%- endfor %}
   net_attributes_map:
     value:
+      ctlplane: {get_param: CtlplaneNetworkAttributes}
       {%- for network in networks if network.enabled|default(true) %}
       {%- set network_name = network.compat_name|default(network.name) %}
       {{network.name_lower}}:

overcloud.j2.yaml

@@ -919,6 +919,7 @@ resources:
     type: OS::Heat::Value
     properties:
       value:
+        ctlplane_mtu: {get_attr: [Networks, net_attributes_map, ctlplane, network, mtu]}
     {%- for network in networks if network.enabled|default(true) and network.name in role.networks|default([]) %}
         {{network.name_lower}}_mtu: {get_attr: [Networks, net_attributes_map, {{network.name_lower}}, network, mtu]}
       {%- if role.networks is mapping %}