Add 'networks_all' ansible group_var

Add a group_var carrying all enabled overcloud
networks. The multi-nic templates should iterate
over all the networks in the order they apper in
network_data.yaml to allow maintaining the
network to nicX contract that existed in the Heat
mulit-nic config templates.

Change-Id: I69fa208d160f1ae2cb2cc252d9b7852ada9e96f0
Related-Bug: #1904894
(cherry picked from commit fe275dd918)

overcloud.j2.yaml

@@ -1047,6 +1047,10 @@ resources:
         {%- for network in networks if network.enabled|default(true) %}
           {{network.name}}: {{network.name_lower}}
         {%- endfor %}
+        networks_all:
+        {%- for network in networks if network.enabled|default(true) %}
+          - {{network.name}}
+        {%- endfor %}
         service_metadata_settings: {get_attr: [{{role.name}}ServiceChainRoleData, value, service_metadata_settings]}
         tripleo_network_config_template: {get_param: {{role.name}}NetworkConfigTemplate}
         tripleo_network_config_with_ansible: {get_param: NetworkConfigWithAnsible}