stop.sh: send sigterm first; then sigkill

I got a crash that forced me to sigkill it, so we'd better not take it
away completely just yet. This should be a good compromise.

(I don't disagree, but:)

It doesn't fail. kill just sends signals and that always succeeds. It's a trickier business to determine what the process actually did with the signal. I'd be put to some trouble to do that and I don't see that it's worth the effort for a temporary hack.