Only update system paths on Spyder startup, not every time the python…

…path manager widget is invoked.

If the system paths have changed since last widget invocation, then the user may not be aware and there is no indication in the widget that there has been a change. Furthermore, canceling the widget may still result in a change to the pythonpath, which would be inconsistent with the cancel action.

spyder/plugins/pythonpath/container.py

@@ -98,7 +98,7 @@ def show_path_manager(self):
             self.path_manager_dialog.update_paths(
                 project_paths=self._project_paths,
                 user_paths=self._user_paths,
-                system_paths=self._get_system_paths(),
+                system_paths=self._system_paths,
                 prioritize=self._prioritize
             )