private CipherOption unwrap(CipherOption option, SaslClient saslClient) throws IOException {
      byte[] inKey = option.getInKey();
      if (inKey != null) {
        inKey = saslClient.unwrap(inKey, 0, inKey.length);
      }
      byte[] outKey = option.getOutKey();
      if (outKey != null) {
        outKey = saslClient.unwrap(outKey, 0, outKey.length);
      }
      return new CipherOption(option.getCipherSuite(), inKey, option.getInIv(), outKey,
        option.getOutIv());
    }
Create a ByteString from byte array without copying (wrap), and then set it as the payload
for the builder.
@param builder builder for HDFS DataTransferEncryptorMessage.
@param payload byte array of payload.
hbase-asyncfs/src/main/java/org/apache/hadoop/hbase/io/asyncfs/FanOutOneBlockAsyncDFSOutputSaslHelper.java