Move thread options into a seperate structure

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/ioengines.c b/ioengines.c
index b18bc9a..0e5ea62 100644
--- a/ioengines.c
+++ b/ioengines.c
@@ -215,7 +215,7 @@
 		int r;
 
 		td->io_u_queued++;
-		if (td->io_u_queued > td->iodepth_batch) {
+		if (td->io_u_queued > td->o.iodepth_batch) {
 			r = td_io_commit(td);
 			if (r < 0)
 				return r;