cgroup: Merge branch 'for-3.11-fixes' into for-3.12

for-3.12 branch is about to receive invasive updates which are
dependent on da0a12caff ("cgroup: fix a leak when percpu_ref_init()
fails").  Given the amount of scheduled changes, I think it'd less
painful to pull in for-3.11-fixes as preparation.  Pull in
for-3.11-fixes into for-3.12.

Signed-off-by: Tejun Heo <tj@kernel.org>