Correct comments to align with the code

public void shutdown() {
...
  while (true) {
    // When shutting down for restart, wait 2.5 seconds before forcing
    // termination of receiver threads.
    if (!this.shutdownForUpgrade ||
        (this.shutdownForUpgrade && (Time.monotonicNow() - timeNotified
            > 1000))) {
      this.threadGroup.interrupt();
      break;
    }