Comment 10 for bug 1470030

For the record, you can enable KillUserProcesses=yes in /etc/systemd/logind.conf to automatically clean up processes which don't properly terminate upon session stop. It has been tried to make this the default, but it met heavy opposition, so we won't do that by default. Reassigning to gnupg2 for now, as gpg-agent needs to properly stop on logout. systemd --user will stop when the last "real" session is gone, and so will lightdm's session child.