sched: rt-group: fix hierarchy

Don't re-set the entity's runqueue to the wrong rq after we've set it
to the right one.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Daniel K. <dk@uw.no>
Signed-off-by: Ingo Molnar <mingo@elte.hu>