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: I5132fd085d6ed617055e41c0502d43f00f3a9af4
Closes-Bug: #1524322

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

@@ -29,6 +29,7 @@ Workflow:
       - $._netExplorer: new(sys:NetworkExplorer)
       - $._networks: null
       - $._subnetworks: null
+      - $._ports: null
       - $._internalNetworkId: null
       - $._internalSubnetworkId: null
       - $._externalNetworkId: null
@@ -57,6 +58,23 @@ 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(
@@ -120,5 +138,3 @@ Workflow:
           netRef: $._internalNetworkId
           subnetRef: $._internalSubnetworkId
           floatingIpNeRef: $._externalNetworkId
-
-

murano/engine/system/net_explorer.py

@@ -187,3 +187,8 @@ class NetworkExplorer(murano_object.MuranoObject):
     def listSubnetworks(self, _context):
         client = self._clients.get_neutron_client(_context)
         return client.list_subnets()['subnets']
+
+    # noinspection PyPep8Naming
+    def listPorts(self, _context):
+        client = self._clients.get_neutron_client(_context)
+        return client.list_ports()['ports']