Add zero_buffers option

This option will cause all IO buffers to be initialized to all zeroes.
The default is to fill them with random data.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/options.c b/options.c
index f8e89f3..754eb81 100644
--- a/options.c
+++ b/options.c
@@ -827,6 +827,12 @@
 		.help	= "Do reporting on a per-group basis",
 	},
 	{
+		.name	= "zero_buffers",
+		.type	= FIO_OPT_STR_SET,
+		.off1	= td_var_offset(zero_buffers),
+		.help	= "Init IO buffers to all zeroes",
+	},
+	{
 		.name = NULL,
 	},
 };