Do not reload a project if project is already opened

Ref https://github.com/GNS3/gns3-gui/issues/1251

gns3server/controller/__init__.py

@@ -217,7 +217,10 @@ class Controller:
         topo_data.pop("revision")
         topo_data.pop("type")
 
-        project = yield from self.add_project(path=os.path.dirname(path), status="closed", filename=os.path.basename(path), **topo_data)
+        if topo_data["project_id"] in self._projects:
+            project = self._projects[topo_data["project_id"]]
+        else:
+            project = yield from self.add_project(path=os.path.dirname(path), status="closed", filename=os.path.basename(path), **topo_data)
         if load:
             yield from project.open()
         return project

gns3server/controller/project.py

@@ -337,6 +337,9 @@ class Project:
         """
         Load topology elements
         """
+        if self._status == "opened":
+            return
+
         self.reset()
         path = self._topology_file()
         if os.path.exists(path):