Bug#818978: systemd crashes in lxc on container stop

[0x2a at correcthorsebatterystaple.xyz]

Hi,

backporting the upstream fix [0] from systemd 219 doesn't seem to 
resolve the issue, but Stéphane Grabers patches [1] do so.

All patches have been tested with current LXC/LXD/lxcfs 2.0.0 RCs with 
debian jessie as host/guest system.

[0] 
https://github.com/systemd/systemd/commit/874d3404cbf2363604106c8f86683db4082691ea
[1] 
https://lists.freedesktop.org/archives/systemd-devel/2015-January/027113.html