Switch MQTT helpers to logging error message instead of error code.
Adds time parameter to xProccessLoop so defender demo does not wait extra time.
Fixes some incorrect returns in metrics_collector.c
* Add submodule pointer to the aws/jobs-for-aws-iot-embedded-sdk repository for the Jobs library
* Commonize the MQTT helper functions used by the Device Shadow demo by re-locating them to FreeRTOS-Plus/Demo/AWS/MQTT_Demo_Helpers and updating the Device Shadow demo to use the new files