http-push.c::remove_locks(): fix use after free

Noticed and reported by Serhat Şevki Dinçer.

Signed-off-by: Alex Riesen <raa.lkml@gmail.com>
Acked-by: Clemens Buchacher <drizzd@aon.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

http-push.c

@@ -1356,8 +1356,9 @@ static void remove_locks(void)
 
 	fprintf(stderr, "Removing remote locks...\n");
 	while (lock) {
+		struct remote_lock *next = lock->next;
 		unlock_remote(lock);
-		lock = lock->next;
+		lock = next;
 	}
 }