Ignore trailing /init.scope in init cgroups

Ignore trailing /init.scope in init cgroups

The lxc monitor does not store the container's cgroups, rather it
recalculates them whenever needed.

Systemd moves itself into a /init.scope cgroup for the systemd
controller.

It might be worth changing that (by storing all cgroup info in the
lxc_handler), but for now go the hacky route and chop off any
trailing /init.scope.

I definately thinkg we want to switch to storing as that will be
more bullet-proof, but for now we need a quick backportable fix
for systemd 226 guests.

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>