title: NotificationListenerService gets killed but never restarted
body: <p>Hi all i'm having troubles with an app that I'm developing. I make use of NotificationListenerService, prompt the user to set the Notification permission from the menu and all works flawlessly. But when I update my app, or when my service gets killed it, for unknown reasons, doesn't restart.
  In <code>onCreate()</code> I retain a reference to the service with <code>instance = this;</code> that I use to determine if my service is running from other classes.</p>
  
  <p>This is some methods in <code>onNotificationPosted(StatusBarNotification notification)</code> that extends NotificationListenerService:</p>
  
  <pre><code>@Override
  public void onNotificationPosted(StatusBarNotification sbn) {
      if (MyOtherService.hasInstance()) {
          Log.v(TAG, "onNotificationPosted called by system");
          int count_debug = 1;
          for (StatusBarNotificationListenerInterface listener : toBeNotified) {
              if(listener != null) {
                  Log.v(TAG, "Loop call #" + count_debug++);
                  listener.onNotificationHotAdded(sbn);
              }
          }
      } else {
          // MyOtherService isn't running. Does nothing but clearing toBeNotified list.
          toBeNotified.clear();
          Log.v(TAG, "onNotificationPosted: MyOtherService is stopped ");
      }
  }
  
  public static void registerForNotifications(StatusBarNotificationListenerInterface listener) {
      if (!toBeNotified.contains(listener)) {
          Log.v(TAG, listener.getClass().getCanonicalName() + " added to toBeNotified list");
          toBeNotified.add(listener);
      }
  }
  </code></pre>
  
  <p>NOTE: MyOtherService extends DreamService and just register itself calling the <code>registerForNotifications()</code> method.</p>
  
  <p>In the <code>MyNotificationListener</code> I override <code>onStartCommand</code> returning <code>START_STICKY</code></p>
  
  <p>I'm really going crazy with this stuff being killed almost at each update.</p>