Fix read_iolog

Caveat - it only works with 1 file, unfortunately. Will need a format
change to get that right.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/io_u.c b/io_u.c
index d5dd84b..99f0728 100644
--- a/io_u.c
+++ b/io_u.c
@@ -289,7 +289,7 @@
 	/*
 	 * If using an iolog, grab next piece if any available.
 	 */
-	if (td->o.read_iolog)
+	if (td->o.read_iolog_file)
 		return read_iolog_get(td, io_u);
 
 	/*