MediaRouter: Fix syncSystemRoutes behavior

- Use a different approach to check whether the audio is routed to
  bluetooth or not.
- Do not select other routes instead of the bluetooth route and
  the default route.
- Uses isSystemLiveAudioOnlyRoute instead of isSystemBluetoothRoute.

Bug: 33791300, Bug: 34645668
Test: Manual with Support7Demos
Change-Id: Id2f798c33b4cef687e930cc990db42f6f351700b
3 files changed