Ensure that we exit with non-zero status on IO engine load failure

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/ioengines.c b/ioengines.c
index 6b677cb..7f4e104 100644
--- a/ioengines.c
+++ b/ioengines.c
@@ -312,6 +312,8 @@
 			log_err("fio: io engine init failed. Perhaps try"
 				" reducing io depth?\n");
 		}
+		if (!td->error)
+			td->error = ret;
 	}
 
 	return ret;