This doesn't affect the functionality of subsequent test runs but it does flood the process tree with useless processes and is a generally bad side effect that we should fix.

All the other daemons we incidentally launch from our private session buses while running these tests exit gracefully on their own (as is the convention for D-Bus-activated daemons). So, the best solution is probably to fix bug#708765. I'm creating this bug to track that that patch would fix the problem and to publicly record that this problem exists.