Missed FIO_UNIDIR io ops flags on net engine

Inadvertenly only set it on the netsplice engine, not net.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/engines/net.c b/engines/net.c
index 0cda953..0adc006 100644
--- a/engines/net.c
+++ b/engines/net.c
@@ -461,7 +461,7 @@
 	.cleanup	= fio_netio_cleanup,
 	.open_file	= fio_netio_open_file,
 	.close_file	= generic_close_file,
-	.flags		= FIO_SYNCIO | FIO_DISKLESSIO,
+	.flags		= FIO_SYNCIO | FIO_DISKLESSIO | FIO_UNIDIR,
 };
 
 static struct ioengine_ops ioengine_splice = {