lib/upnp: Fix port order

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/2980

lib/osutil/mkdirall_windows.go

@@ -25,7 +25,11 @@ func MkdirAll(path string, perm os.FileMode) error {
 		if dir.IsDir() {
 			return nil
 		}
-		return &os.PathError{"mkdir", path, syscall.ENOTDIR}
+		return &os.PathError{
+			Op:   "mkdir",
+			Path: path,
+			Err:  syscall.ENOTDIR,
+		}
 	}
 
 	// Slow path: make sure parent exists and then call Mkdir for path.