Pull more cgroup updates from Tejun Heo:
 "I forgot to include the patches which got applied to for-4.7-fixes
  late during last cycle.

  Eric's three patches fix bugs introduced with the namespace support"

* 'for-4.7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroupns: Only allow creation of hierarchies in the initial cgroup namespace
  cgroupns: Close race between cgroup_post_fork and copy_cgroup_ns
  cgroupns: Fix the locking in copy_cgroup_ns