Improve public network detection algorithm

It is possible that there are several public networks exist.
ExistingNeutronNetwork used to pick first one of them.
Now when internal network name or ID supplied it tries
to find such public network that the internal network has
a common router with.

Change-Id: I252bb5545891903355cf7f8480a2cd76febcfebe
Closes-Bug: #1524322

meta/io.murano/Classes/resources/ExistingNeutronNetwork.yaml

@@ -41,6 +41,7 @@ Workflow:
       - $._netExplorer: new(sys:NetworkExplorer)
       - $._networks: null
       - $._subnetworks: null
+      - $._ports: null
       - $._internalNetworkId: null
       - $._internalSubnetworkId: null
       - $._externalNetworkId: null
@@ -69,6 +70,23 @@ Workflow:
               $.id = $this.internalSubnetworkName) and
                 $.network_id = $this._internalNetworkId).first().id
 
+      - If: $.externalNetworkName = null and $._internalNetworkId != null
+        Then:
+          - $ports: $._netExplorer.listPorts()
+          - $routerCandidates: $ports.where(
+              $.network_id = $this._internalNetworkId and $.device_owner = 'network:router_interface').
+              select($.device_id)
+          - $networkCandidates: $ports.where(
+              $.device_id in $routerCandidates and $.network_id != $this._internalNetworkId).
+              select($.network_id)
+          - $externalNetwork: $._getNetworks().where(
+              $.get('router:external') = true and $.id in $networkCandidates).
+              firstOrDefault()
+          - If: $externalNetwork != null
+            Then:
+              - $.externalNetworkName: $externalNetwork.name
+              - $._externalNetworkId: $externalNetwork.id
+
       - If: $.externalNetworkName = null
         Then:
           $.externalNetworkName: $._getNetworks().where(
@@ -123,11 +141,10 @@ Workflow:
             floatingIpNetRef => $floatingIpNetRef
           )
 
-
   describe:
     Body:
       - $.deploy()
-      - $subnet: $._netExplorer.listSubnetworks().where(
+      - $subnet: $._getSubnetworks.where(
             $.network_id = $this._internalNetworkId).first()
       - Return:
           provider: Neutron

murano/engine/system/net_explorer.py

@@ -175,3 +175,7 @@ class NetworkExplorer(object):
     def list_subnetworks(self):
         client = self._clients.get_neutron_client()
         return client.list_subnets()['subnets']
+
+    def list_ports(self):
+        client = self._clients.get_neutron_client()
+        return client.list_ports()['ports']