Enable show in file manager for cloud

Fix https://github.com/GNS3/gns3-gui/issues/1900

gns3server/schemas/cloud.py

@@ -75,7 +75,7 @@ CLOUD_CREATE_SCHEMA = {
                      {"$ref": "#/definitions/HostInterfaces"}
                  ]},
             ]
-        },
+        }
     },
     "additionalProperties": False,
     "required": ["name"]
@@ -123,6 +123,10 @@ CLOUD_OBJECT_SCHEMA = {
                  ]},
             ]
         },
+        "node_directory": {
+            "description": "Path to the VM working directory",
+            "type": "string"
+        },
         "status": {
             "description": "Node status",
             "enum": ["started", "stopped", "suspended"]