@Override
    protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
      msg.skipBytes(4);
      byte[] b = new byte[msg.readableBytes()];
      msg.readBytes(b);
      ctx.fireChannelRead(Unpooled.wrappedBuffer(saslClient.unwrap(b, 0, b.length)));
    }
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