The scanner order for memstore scanners are wrong

  /**
   * Get the order of this KeyValueScanner. This is only relevant for StoreFileScanners and
   * MemStoreScanners (other scanners simply return 0). This is required for comparing multiple
   * files to find out which one has the latest data. StoreFileScanners are ordered from 0
   * (oldest) to newest in increasing order. MemStoreScanner gets LONG.max since it always
   * contains freshest data.
   */
  long getScannerOrder();