relay: fix cpu offline problem

relay_open() will close allocated buffers when failed.
but if cpu offlined, some buffer will not be closed.
this patch fixed it.

and did cleanup for relay_reset() too.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>