sched/fair: Update overutilized status after migrating tasks

The enqueue_task_fair updates the overutilized status only for
waking tasks. Since multiple tasks may get migrated during the
load balancer, update the overutilized status after migrating
all tasks.

Change-Id: I2163ba8dcb7eb9677f609d19e3579867e4dff1b1
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>