staging: lustre: osc: osc_extent_wait() shouldn't be interruptible

Otherwise it will hit the assertion at cl_lock.c:

 cl_lock.c:1967:discard_cb())
  ASSERTION( (!(page->cp_type == CPT_CACHEABLE) ||
  (!PageWriteback(cl_page_vmpage(env, page)))) ) failed:

This is because in osc_lock_flush() we have to make sure the IO
is finished before discarding the pages.
Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-2779
Reviewed-on: http://review.whamcloud.com/5419Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/osc/osc_cache.c

@@ -965,7 +965,7 @@ static int osc_extent_wait(const struct lu_env *env, struct osc_extent *ext,
 			"%s: wait ext to %d timedout, recovery in progress?\n",
 			osc_export(obj)->exp_obd->obd_name, state);
 
-		lwi = LWI_INTR(LWI_ON_SIGNAL_NOOP, NULL);
+		lwi = LWI_INTR(NULL, NULL);
 		rc = l_wait_event(ext->oe_waitq, extent_wait_cb(ext, state),
 				  &lwi);
 	}