Add log_valist()

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/debug.c b/debug.c
index 2eb3b6f..9722878 100644
--- a/debug.c
+++ b/debug.c
@@ -22,6 +22,6 @@
 	log_info("%-5u ", (int) pid);
 
 	va_start(args, str);
-	vfprintf(f_out, str, args);
+	log_valist(str, args);
 	va_end(args);
 }