restore ContentApi.__real_base_query default behaviour

tracim/tracim/lib/content.py

         if workspace:
             result = result.filter(Content.workspace_id==workspace.workspace_id)
 
-        if self._user and workspace and not self._disable_user_workspaces_filter:
+        if self._user and not self._disable_user_workspaces_filter:
             user = DBSession.query(User).get(self._user_id)
             # Filter according to user workspaces
             workspace_ids = [r.workspace_id for r in user.roles \