message: [backup] trivial: name fix
  Closes:
  Approved by: wqfish
diff: @@ -42,15 +42,15 @@ fn tmp_db_with_random_content() -> (TempPath, LibraDB) {
  #[test]
  fn end_to_end() {
  - let (_src_db_dir, db_src) = tmp_db_with_random_content();
  - let db_src = Arc::new(db_src);
  + let (_src_db_dir, src_db) = tmp_db_with_random_content();
  + let src_db = Arc::new(src_db);
  let tgt_db_dir = TempPath::new();
  let backup_dir = TempPath::new();
  backup_dir.create_as_dir().unwrap();
  let adaptor = LocalStorage::new(backup_dir.path().to_path_buf());
  let config = NodeConfig::random();
  - let mut rt = start_backup_service(config.storage.backup_service_port, db_src);
  + let mut rt = start_backup_service(config.storage.backup_service_port, src_db);
  let client = BackupServiceClient::new(config.storage.backup_service_port);
  let (version, state_root_hash) = rt.block_on(client.get_latest_state_root()).unwrap();
  let handles = rt
  