mqtt.loop_start() method has issues on Linux Machines

[mlevine324]

Applications currently have a start_up method that uses paho mqtt's loop_start() function, but for some reason on Linux machines only the background process is terminated after initial connect (i.e. does connect but immediately disconnects). Issue is resolved by using the loop_forever() method instead. Consider adjusting start_up for v2.0 release.

[TheoSherman29]

A slightly less hack-y solution I've begun using is rather than have an infinite while loop that must be terminated manually, I use a loop that checks if the simulator Mode is TERMINATED and allows the application to terminate then. This also allows for the applications to execute code after the simulation completes, such as writing data to a file to be post-processed by another application