drbd: fix if(); found by kbuild test robot

Recently introduced al_begin_io_nonblock() was returning -EBUSY,
even when it should return -EWOULDBLOCK.

Impact:
A few spurious wake_up() calls in prepare_al_transaction_nonblock().

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
index 6afe173..6608076 100644
--- a/drivers/block/drbd/drbd_actlog.c
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -389,7 +389,7 @@
 		if (unlikely(tmp != NULL)) {
 			struct bm_extent  *bm_ext = lc_entry(tmp, struct bm_extent, lce);
 			if (test_bit(BME_NO_WRITES, &bm_ext->flags)) {
-				if (!test_and_set_bit(BME_PRIORITY, &bm_ext->flags));
+				if (!test_and_set_bit(BME_PRIORITY, &bm_ext->flags))
 					return -EBUSY;
 				return -EWOULDBLOCK;
 			}