Retrieve next file to service in get_io_u()

This improves requeue handling, we don't want to inadvertently
skip a file because we requeue an io_u.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.h b/fio.h
index baaa9a8..12afa06 100644
--- a/fio.h
+++ b/fio.h
@@ -609,7 +609,7 @@
  */
 #define queue_full(td)	list_empty(&(td)->io_u_freelist)
 extern struct io_u *__get_io_u(struct thread_data *);
-extern struct io_u *get_io_u(struct thread_data *, struct fio_file *);
+extern struct io_u *get_io_u(struct thread_data *);
 extern void put_io_u(struct thread_data *, struct io_u *);
 extern void requeue_io_u(struct thread_data *, struct io_u **);
 extern long io_u_sync_complete(struct thread_data *, struct io_u *, endio_handler *);