Make exit_used.py compatible with asyncio
Honestly this is probably somewhat a step backward because if I return to Stem
I plan to substantially revert the asyncio migration, but for now simply fixing
the script. With the current codebase it fails with...
% python exit_used.py
Tracking requests for tor exits. Press 'enter' to end.
stem/stem/control.py:4004: RuntimeWarning: coroutine 'Controller.get_circuit' was never awaited
log.warn('Event listener raised an uncaught exception (%s): %s' % (exc, event))