sched: Do not stop cpu in set_cpus_allowed_ptr() if task is not running

If a task is queued but not running on it rq, we can simply migrate
it without migration thread and switching of context.

Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1410519814.3569.7.camel@tkhai
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --cc kernel/sched/core.c
Simple merge