Fix an issue with editing network on windows

Fix  #982

gns3server/handlers/api/controller/node_handler.py

@@ -20,6 +20,7 @@ import aiohttp
 
 from gns3server.web.route import Route
 from gns3server.controller import Controller
+from gns3server.utils import force_unix_path
 
 from gns3server.schemas.node import (
     NODE_OBJECT_SCHEMA,
@@ -337,7 +338,7 @@ class NodeHandler:
         project = yield from Controller.instance().get_loaded_project(request.match_info["project_id"])
         node = project.get_node(request.match_info["node_id"])
         path = request.match_info["path"]
-        path = os.path.normpath(path)
+        path = force_unix_path(path)
 
         # Raise error if user try to escape
         if path[0] == ".":