sched,cgroup: Fix up task_groups list

With multiple instances of task_groups, for_each_rt_rq() is a noop,
no task groups having been added to the rt.c list instance.  This
renders __enable/disable_runtime() and print_rt_stats() noop, the
user (non) visible effect being that rt task groups are missing in
/proc/sched_debug.

Change-Id: Ib337ebda0e752f838d787c03fe1b0a8f03ea0551
Signed-off-by: Mike Galbraith <efault@gmx.de>
Cc: stable@kernel.org # v3.3+
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1344308413.6846.7.camel@marge.simpson.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Git-commit: 35cf4e50b16331def6cfcbee11e49270b6db07f5
Git-repo: git://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>