add note that db upgrade code path is br0ken

src/addons.js

@@ -644,6 +644,8 @@ function importDatabase(addon, callback) {
                 if (!error) return iteratorCallback();
 
                 debug(`importDatabase: Error importing ${addon} of app ${app.id}. Marking as errored`, error);
+                // FIXME: there is no way to 'repair' if we are here. we need to make a separate apptask that re-imports db
+                // not clear, if repair workflow should be part of addon or per-app
                 appdb.update(app.id, { installationState: apps.ISTATE_ERROR, error: { message: error.message } }, iteratorCallback);
             });
         }, callback);