dm exception store: fix init error path

Call the correct exit function on failure in dm_exception_store_init.
Signed-off-by: Andrei Warkentin <andrey.warkentin@gmail.com>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

drivers/md/dm-exception-store.c

@@ -283,7 +283,7 @@ int dm_exception_store_init(void)
 	return 0;
 
 persistent_fail:
-	dm_persistent_snapshot_exit();
+	dm_transient_snapshot_exit();
 transient_fail:
 	return r;
 }