Issue #879076 by alex_b, pillarsdotnet, ceardach: Fixed Do not set expired=0...

Issue #879076 by alex_b, pillarsdotnet, ceardach: Fixed Do not set expired=0 where expired is already 0 (performance).

modules/system/system.module

@@ -3018,6 +3018,7 @@ function system_cron() {
     ->fields(array(
       'expire' => 0,
     ))
+    ->condition('expire', 0, '<>')
     ->condition('expire', REQUEST_TIME, '<')
     ->execute();
 }