Latest commit a0ee734 Nov 30, 2016 @njam njam Change systemd KillMode to "mixed"
Possible values are:
- control-group: all remaining processes in the control group of this unit will be killed on unit stop
- process: only the main process itself is killed
- mixed: the SIGTERM signal is sent to the main process while the subsequent SIGKILL signal is sent to all remaining processes of the unit's control group

See https://www.freedesktop.org/software/systemd/man/systemd.kill.html#KillMode=

The current value of "process" will overlook any remaining forked/daemonized processes. When stopping or restarting such a process, child processes can become zombies.
 When instead using "mixed" systemd will send a SIGKILL signal to all remaining processes of the same control group, and thus prevent zombies.
 We should always try to prevent zombies.