Ensure we stop parsing and exit if a command line option fails

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/init.c b/init.c
index ff9b6d4..b330925 100644
--- a/init.c
+++ b/init.c
@@ -1716,6 +1716,8 @@
 			}
 
 			ret = fio_cmd_option_parse(td, opt, val);
+			if (ret)
+				do_exit++;
 
 			if (!ret && !strcmp(opt, "ioengine")) {
 				free_ioengine(td);