Fix / update systemd in Debian Jessie LXC container

# fix Debian Jessie LXC container boot error:
Failed to install release agent, ignoring: No such file or directory
Failed to create root cgroup hierarchy: Invalid argument
Failed to allocate manager object: Invalid argument
# list all container with uses Debian Jessie:
grep -l jessie /var/lib/lxc/*/rootfs/etc/os-release
# set container name
# stop container
lxc-stop -n ${CONTAINER} -t 10
# backup container
tar -C /var/lib/lxc --use-compress-program=pbzip2 -cf ${CONTAINER}.$(date -I).tar.bz2 ${CONTAINER}
# upgrade systemd in container
echo "deb stretch main" > /var/lib/lxc/${CONTAINER}/rootfs/etc/apt/sources.list.d/stretch.list
chroot /var/lib/lxc/${CONTAINER}/rootfs/ apt-get update
chroot /var/lib/lxc/${CONTAINER}/rootfs/ apt-get install -y systemd
rm /var/lib/lxc/${CONTAINER}/rootfs/etc/apt/sources.list.d/stretch.list
chroot /var/lib/lxc/${CONTAINER}/rootfs/ apt-get update
# start container
lxc-start -n ${CONTAINER}