Implement connection handover LLCP service.

The Connection Handover specification dictates that we should
exchange Hr/Hs records over a dedicated LLCP service. This adds
the service, and starts using it by default. It will fall back
to the SNEP GET method to remain compatible with Android 4.1
devices. SNEP GET on these devices will return "Not Implemented",
also per the SNEP spec.

Also fixed a bug in endianness of the OOB record.

Bug: 6759842
Change-Id: Ifd360f556bf0e1757eb8bbaadf11efa094aefcf6