update mqttd main.c, fix debug with java bug for JSON with \0 bug

guowenxue

2019-08-03 2f6051f61e62ac477622f02708cb8eb13bc0ca51

tools/rpi_crosstool.tar.bz2 does not exist in tree b75cf047145e4f9eb024d6f0a438a745c2e8c617