Make verify_dump off by default

It's a change of behaviour, so it should be off by default.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/HOWTO b/HOWTO
index ef8f959..41edcf1 100644
--- a/HOWTO
+++ b/HOWTO
@@ -981,7 +981,7 @@
 verify_dump=bool	If set, dump the contents of both the original data
 		block and the data block we read off disk to files. This
 		allows later analysis to inspect just what kind of data
-		corruption occurred. On by default.
+		corruption occurred. Off by default.
 
 verify_async=int	Fio will normally verify IO inline from the submitting
 		thread. This option takes an integer describing how many