@Override
  public RegionScannerImpl getScanner(Scan scan, List<KeyValueScanner> additionalScanners)
    throws IOException {
    return getScanner(scan, additionalScanners, HConstants.NO_NONCE, HConstants.NO_NONCE);
  }
Method to safely get the next sequence number.
@return Next sequence number unassociated with any actual edit.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java