Move the iodepth_batch into td_io_queue() instead

The previous part in do_io() introduced a bug (overwriting ret),
and we really need to do it from other locations as well.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/ioengines.c b/ioengines.c
index 2cc3288..14b15cc 100644
--- a/ioengines.c
+++ b/ioengines.c
@@ -216,8 +216,16 @@
 
 	ret = td->io_ops->queue(td, io_u);
 
-	if (ret == FIO_Q_QUEUED)
+	if (ret == FIO_Q_QUEUED) {
+		int r;
+
 		td->io_u_queued++;
+		if (td->io_u_queued > td->iodepth_batch) {
+			r = td_io_commit(td);
+			if (r < 0)
+				return r;
+		}
+	}
 
 	if ((td->io_ops->flags & FIO_SYNCIO) == 0) {
 		fio_gettime(&io_u->issue_time, NULL);