sched/fair: Reduce local_group logic

Try and reduce the local_group logic by pulling most of it into
update_sd_lb_stats.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-mgezl354xgyhiyrte78fdkpd@git.kernel.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>