[docker-engine] fix systemd shutdown hang (#2451)

When rebooting without the platform_reboot plugin, systemd takes a few
minutes to properly shutdown. It's blocking on some docker cleanup
operation.

As described by docker/for-linux#421 there
is a race between docker.service and containerd.service.
docker needs containerd to properly stop the containers.

build_debian.sh

@@ -182,6 +182,8 @@ sudo LANG=C chroot $FILESYSTEM_ROOT apt-get -y remove software-properties-common
 sudo mkdir -p $FILESYSTEM_ROOT/etc/systemd/system/docker.service.d/
 ## Note: $_ means last argument of last command
 sudo cp files/docker/docker.service.conf $_
+## Fix systemd race between docker and containerd
+sudo sed -i '/After=/s/$/ containerd.service/' $FILESYSTEM_ROOT/lib/systemd/system/docker.service
 
 ## Create default user
 ## Note: user should be in the group with the same name, and also in sudo/docker group