ci/crosvm: Terminate the previous crosvm after a deqp-runner timeout.

When deqp-runner times out, it kills the deqp process, which in our case is the previous invocation of our shell script, so the crosvm and socat cleanup never happened. crosvm has a way to cleanly shut down a previous crosvm invocatino, so let's just use that and do our cleanup when we need to.