Threads created by the master need to be gracefully terminated

[viveksubbarao]

There is no code to terminate the threads created by the server. Code to handle interrupts and other exceptions needs to be put in place so that all resources including threads are terminated and released gracefully.

[drinkbeer]

I guess it's caused by deadlock of two "while 1", one is in line 54, master.py, another one is in line 57, heartbeat.py.