When systemd restarts the transmission-openvpn container, it seems to
leave zombie processes as below.
$ ps uaxww | grep Z
root 1872 0.0 0.0 0 0 ? Z 08:58 0:00 [transmission-da] <defunct>
The zombies do appear to be cleaned up by restarting docker itself, or
by stopping the transmission-openvpn service.
This is an attempt to prevent zombies being spawned via Yelp's
dumb-init, which correctly handles the signals that PID1 gets.
See: https://github.com/Yelp/dumb-init
Dave Webb