Add ->done variable to force exit when we know we are done

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/log.c b/log.c
index cc90f43..7a3327e 100644
--- a/log.c
+++ b/log.c
@@ -91,6 +91,7 @@
 		return 0;
 	}
 
+	td->done = 1;
 	return 1;
 }