cgroup: nested cgroups aren't really supported
cgroup: nested cgroups aren't really supported

After some discussion with Serge Hallyn, it seems that the current
implementation of cgroup namespaces doesn't really support nesting. It's
not a quick fix, so let's disable this for now (not that it matters, since
probably nobody is nesting these anyways right now :)

Signed-off-by: Tycho Andersen <10c18fcb898ee6b17d6575d444b125d10b3f4d6a@canonical.com>
Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@virtuozzo.com>

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