[PATCH] Modify xio_ev_loop_stop() to be level based
 so that any instance inside the xio_ev_loop_run() or the following entry
 into it will definitely break.
 This makes xio_ev_loop_stop() safe to use from other thread which are
 not the running context of this loop_hndl.

Signed-off-by: Eyal Salomon <esalomon@mellanox.com>