Issue time fixup for guasi/libaio

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/engines/libaio.c b/engines/libaio.c
index e6b926c..18dcf9d 100644
--- a/engines/libaio.c
+++ b/engines/libaio.c
@@ -118,6 +118,9 @@
 	struct timeval now;
 	unsigned int i;
 
+	if (!fio_fill_issue_time(td))
+		return;
+
 	fio_gettime(&now, NULL);
 
 	for (i = 0; i < nr; i++) {