message: Need to use RemoveFile to delete files now
diff: @@ -344,7 +344,7 @@ void StorageManager::CreateCheckpoint(int iteration) {
  FileSystem::RemoveDirectory(other_storage_path);
  }
  if (FileSystem::FileExists(other_wal_path)) {
  - FileSystem::RemoveDirectory(other_wal_path);
  + FileSystem::RemoveFile(other_wal_path);
  }
  transaction->Rollback();
  }
  