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.

Signed-off-by: Thomas Stilwell <stilwellt@openlabs.co>
Merge pull request #456 from benemorius/sigkill

stop.sh: send sigterm first; then sigkill