Call startService() in Music Demo

1. Call startService() and the corresponding delayed stopSelf() to
ensure that the service survives a UI/app unbind and the music
continues to play in the background.
2. Add current package as a trusted source for using MediaBrowserService
say with a UI.
3. Minor fix for LogHelper to print messages.

Address review comments from Erik

Bug: 18026217
Change-Id: I8919dcc4d8b24b30e3d7cc70b76b342ac7580ef4