Consolidate disk util, eta, and status check thread

We don't need two, we can just have one do everything.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/diskutil.c b/diskutil.c
index c5c5ea6..51da8a0 100644
--- a/diskutil.c
+++ b/diskutil.c
@@ -117,7 +117,7 @@
 
 	fio_mutex_down(disk_util_mutex);
 
-	if (!disk_util_exit) {
+	if (!helper_exit) {
 		flist_for_each(entry, &disk_list) {
 			du = flist_entry(entry, struct disk_util, list);
 			update_io_tick_disk(du);