update runner tests to send interrupt

[charlierudolph]

This will trigger the shutdown which we can wait for to complete. Hopefully cause our tests to run more reliably since we properly shut down all containers. With this I think we could remove the step of kill all containers in our after scenario.

I think to start we should just use the "And I stop all running processes" in more places and update it to send the signal and wait instead of killing the process.

@hugobho @cheahuychou @mcharawi thoughts?

[hugoesthere]

Yes this would work, but only for Docker processes booted up by exo run right? Are there any other Docker processes run in tests that don't use exo run?