message: FlatFile: close file before rename
diff: @@ -116,6 +116,8 @@ bool FlatFile::add(Identifier id, const Bytes &block) {
  return false;
  }
  + file->close();
  +
  boost::system::error_code error_code;
  boost::filesystem::rename(tmp_file_name, file_name, error_code);
  if (error_code != boost::system::errc::success) {
  