pandad: reset safety mode on exit

[adeebshihadeh]

allows for restarting the device while onroad without faulting the car

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[sshane]

When creating a new Python process with multiprocessing.Process, it inherits the parent's signal handler. For manager, that is to cause a SystemExit immediately, which SIGKILLs pandad.cc before it has a chance to react to the SIGTERM and close the relay.

openpilot/system/manager/manager.py

Lines 183 to 184 in e8857a6

	# SystemExit on sigterm
	signal.signal(signal.SIGTERM, lambda signum, frame: sys.exit(1))

[sshane]

The time between the two pandad stop calls is anywhere between 1 and 2s, so this is already plenty of time to receive the signal and close the relay, no extra sleeps are needed at this time:

openpilot/system/manager/manager.py

Lines 105 to 110 in cb6eb4f

	for p in managed_processes.values():
	p.stop(block=False)
	# ensure all are killed
	for p in managed_processes.values():
	p.stop(block=True)