message: refactor: Use C++11 range-based for loop
diff: @@ -623,8 +623,8 @@ bool BerkeleyDatabase::PeriodicFlush()
  if (!lockDb) return false;
  // Don't flush if any databases are in use
  - for (auto it = env->mapFileUseCount.begin() ; it != env->mapFileUseCount.end(); it++) {
  - if ((*it).second > 0) return false;
  + for (const auto& use_count : env->mapFileUseCount) {
  + if (use_count.second > 0) return false;
  }
  // Don't flush if there haven't been any batch writes for this database.
  