smoke.py should have a signal handler to dump a stack trace

smoke.py should setup a signal handler to dump its stack trace, so if its stuck we can debug it by doing something like

kill -3 <pid>

good example of how to do this here: http://stackoverflow.com/questions/132058/showing-the-stack-trace-from-a-running-python-application

this command could be added to the timeout handler in MCI so that we get info on what smoke.py is doing when an MCI test suite hangs.

cc Mark Benvenuto