Revert "kernel: cgroup_timer_slack: Adaptations for 3.4 kernel"

This reverts commit 249631cbbdff6461d8ec17b83a63c69be577edef.
Revert "cgroups: timer_slack: forward port timer_slack to 3.4. http://lwn.net/Articles/431847/"

This reverts commit cdb21cff8112f01dc9195ae9e6d082f0dae65f78.