sched/fair: fix to set sgs->group_misfit_task

In current code after meets two conditions to set
sgs->group_misfit_task:

- Condition 1: the CPU is overutilized;
- Condition 2: rq->misfit is set;

But if we think about there have corner case that CPU level signal has
not been increased over tipping point but it has one big task is
migrated onto this CPU so rq->misfit flag has been set. For this case,
we will miss to set sgs->group_misfit_task due condition 1 should take
very long time to become true.

This patch is to directly check if rq->misfit flag has been set and then
directly to set sgs->group_misfit_task. So give more chance for misfit
task migration.

Change-Id: If5723788390864a130f29d81529f8310efc76299
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Patch-mainline: eas-dev @ 12/22/16, 15:58
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>