We already reschedule env.dst_cpu in attach_tasks()->check_preempt_curr()
if this is necessary.

Furthermore, a higher priority class task may be current on dest rq,
we shouldn't disturb it.
Signed-off-by: NKirill Tkhai <ktkhai@parallels.com>
Cc: Juri Lelli <juri.lelli@gmail.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20140930210441.5258.55054.stgit@localhostSigned-off-by: NIngo Molnar <mingo@kernel.org>