private void sendSaslMessage(ChannelHandlerContext ctx, byte[] payload) throws IOException {
      sendSaslMessage(ctx, payload, null);
    }
Creates a new SaslClientCallbackHandler.
@param userName SASL user name
@param password SASL password
hbase-asyncfs/src/main/java/org/apache/hadoop/hbase/io/asyncfs/FanOutOneBlockAsyncDFSOutputSaslHelper.java