Narek Ghazaryan

`FreeRTOS_read` returns 0 in [MQTTFreeRTOS.c](https://github.com/eclipse/paho.mqtt.embedded-c/blob/master/MQTTClient-C/src/FreeRTOS/MQTTFreeRTOS.c), when timeout has accrued, which caused returning of -1 value of `MQTTYield`. I think it would be right to add a handler for this case...