Move the generation of the list of ports to the server

Ref #676

tests/topologies/1_5_cloud/after/1_5_cloud.gns3

@@ -30,10 +30,13 @@
                 "name": "Cloud 1",
                 "node_id": "ANYUUID",
                 "node_type": "cloud",
+                "port_name_format": "Ethernet{0}",
+                "port_segment_size": 0,
+                "first_port_name": null,
                 "properties": {
                     "interfaces": [
                     ],
-                    "ports": [
+                    "ports_mapping": [
                         {
                             "interface": "bridge0",
                             "name": "bridge0",