Fix QBluetoothDeviceDiscovery unit test for Bluez 5

Change-Id: Icae08c1963512e38ba438bd905f5629fa2e40422
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Ensure that QBluetoothAddress debug operator can handle const refs

This operator is new in Qt 5.4 and therefore can be changed at this
stage.

Change-Id: I679707515fd7053aae6077460f99921c18717578
Reviewed-by: Kai Koehne <kai.koehne@digia.com>