Android: Lots of QBluetoothServiceDiscoveryAgent bug fixes

1.) Don't crash if Android's UUID message doesn't contain a uuid parcel

2.) Sanitize the behavior if Bt device is turned on/off while doing SDP
discovery

3.) Don't even start discovery process if the Bt device is turned off

4.) Don't add duplicate entries to discoveredServices()

5.) Properly process UUID messages from Android OS

Change-Id: I195363820f5762a2551b3c6c3e983ae2a83c7374
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>