message: Add missing lock to CDB Flush
diff: @@ -294,6 +294,7 @@ void CDB::Flush()
  if (fReadOnly)
  nMinutes = 1;
  + LOCK(bitdb.cs_db);
  bitdb.dbenv->txn_checkpoint(nMinutes ? GetArg("-dblogsize", DEFAULT_WALLET_DBLOGSIZE) * 1024 : 0, nMinutes, 0);
  }
  