client/server: add support for passing disk_util structures

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/stat.c b/stat.c
index f77e7b6..6377869 100644
--- a/stat.c
+++ b/stat.c
@@ -949,7 +949,12 @@
 				show_group_stats(rs);
 		}
 
-		show_disk_util();
+		if (is_backend)
+			fio_server_send_du();
+		else
+			show_disk_util();
+
+		free_disk_util();
 	}
 
 	free(runstats);