message: refactor timer calibration mechanism
diff: @@ -223,16 +223,7 @@ int swTimer_select(swTimer *timer)
  //persistent timer
  if (tnode->interval > 0 && !tnode->remove)
  {
  - int64_t _now_msec = swTimer_get_relative_msec();
  - if (_now_msec <= 0)
  - {
  - tnode->exec_msec = now_msec + tnode->interval;
  - }
  - else if (tnode->exec_msec + tnode->interval < _now_msec)
  - {
  - tnode->exec_msec = _now_msec + tnode->interval;
  - }
  - else
  + while (tnode->exec_msec <= now_msec)
  {
  tnode->exec_msec += tnode->interval;
  }
  