title: BackHandler.exitApp() is not closing the services of react-native android app
body: <p>When I am using <code>BackHandler.exitApp()</code> to close the app and not removing the app from task manager window of the android, when I am again opening the app, it seems before it starts the service init, it start to call service functions. 
  So as a result, I am doing init of <code>this.db = new Datastore({ filename: dbPath, autoload: true, ...options });</code> , But before it happens the database service is already trying to use <code>this.db</code>, so, as a result, it is saying <code>this.db</code> as <code>undefined</code>.</p>
  
  <p>Can anyone tell me how can I do the init first and then start the services everytime I open the app? Or how can I exit a react native app with completely kill all the tasks?</p>