return FAILURE asap when readPacket fails in cycle
return FAILURE asap when readPacket fails in cycle

Signed-off-by: Steve Song <0cfa65d07d0d149e9ff97d894086f7acab1bdc09@gmail.com>

monstrenyatko/ArduinoMqtt,monstrenyatko/ArduinoMqtt,eclipse/paho.mqtt.embedded-c,eclipse/paho.mqtt.embedded-c,eclipse/paho.mqtt.embedded-c,eclipse/paho.mqtt.embedded-c,eclipse/paho.mqtt.embedded-c