Fix double io_u free on error in do_verify()

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.c b/fio.c
index 3191a7d..ae89bb9 100644
--- a/fio.c
+++ b/fio.c
@@ -310,9 +310,6 @@
 			break;
 	}
 
-	if (io_u)
-		put_io_u(td, io_u);
-
 	if (td->cur_depth)
 		cleanup_pending_aio(td);