Correct link are not connected to the correct ethernet switch port after conversion

Fix https://github.com/GNS3/gns3-gui/issues/1797

tests/topologies/1_5_builtins/after/builtins.gns3

@@ -14,7 +14,23 @@
             }
         ],
         "drawings": [],
-        "links": [],
+        "links": [
+          {
+            "link_id": "ANYUUID",
+            "nodes": [
+              {
+                "port_number": 1,
+                "node_id": "ANYUUID",
+                "adapter_number": 0
+              },
+              {
+                "port_number": 1,
+                "node_id": "ANYUUID",
+                "adapter_number": 0
+              }
+            ]
+          }
+        ],
         "nodes": [
             {
                 "compute_id": "local",

tests/topologies/1_5_builtins/before/builtins.gns3

@@ -4,6 +4,16 @@
     "project_id": "644e3892-4a50-4457-9601-2234d4842169",
     "revision": 4,
     "topology": {
+        "links": [
+            {
+                "description": "",
+                "destination_node_id": 3,
+                "destination_port_id": 10,
+                "id": 1,
+                "source_node_id": 2,
+                "source_port_id": 2
+            }
+        ],
         "nodes": [
             {
                 "description": "ATM switch",