static Encryptor createEncryptor(Configuration conf, HdfsFileStatus stat, DFSClient client)
    throws IOException {
    FileEncryptionInfo feInfo = stat.getFileEncryptionInfo();
    if (feInfo == null) {
      return null;
    }
    return TRANSPARENT_CRYPTO_HELPER.createEncryptor(conf, feInfo, client);
  }
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