sched: Update task->on_rq when tasks are moving between runqueues

Task->on_rq has three states:
	0 - Task is not on runqueue (rq)
	1 (TASK_ON_RQ_QUEUED) - Task is on rq
	2 (TASK_ON_RQ_MIGRATING) - Task is on rq but in the
	process of being migrated to another rq

When a task is moving between rqs task->on_rq state should be
TASK_ON_RQ_MIGRATING

CRs-fixed: 884720
Change-Id: I1572aba00a0273d4ad5bc9a3dd60fb68e2f0b895
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>