title: MediaRouteButton State unstable in FragmentActivity
body: <p>How to keep MediaRouteButton state and avoid disabled state on FragmentActivity</p>
  
  <p>I have written a service to handle all cast sdk logic on fragment activities in my project. When created that MediaRouteButton is enabled and I'm able to connect but if I disconnect from cast device or do not select a device soon enough, the button is disabled and is shown in grey color. It may be related with the default route connection. I have tried setting a mediaRouteSelector and also leaving it with the default one. How to keep the MediaRouteButton state and keep it enabled. (Chromecast device is present in the same network, registered as dev device with the receiver ID etc)</p>
  
  <pre><code>// mButton.routeSelector = mediaRouteSelector
  CastButtonFactory.setUpMediaRouteButton(activity, mButton)
  if(castContext == null) castContext = CastContext.getSharedInstance(activity.applicationContext)
  setUpButton(castContext!!.castState, mButton)
  
  Expected: MediaRouteButton state is kept (disabled avoided)
  Actual: The MediaRouteButton is enabled and works for a while then disabled.
  </code></pre>