iolog bug: TD_DDIR_READ should be TD_DDIR_WRITE

It's a typo, if we don't have reads stored but writes, then the
global direction should naturally be TD_DDIR_WRITE.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/log.c b/log.c
index fbc407d..c0e9d4a 100644
--- a/log.c
+++ b/log.c
@@ -158,7 +158,7 @@
 	else if (reads && !writes)
 		td->o.td_ddir = TD_DDIR_READ;
 	else if (!reads && writes)
-		td->o.td_ddir = TD_DDIR_READ;
+		td->o.td_ddir = TD_DDIR_WRITE;
 	else
 		td->o.td_ddir = TD_DDIR_RW;