Serial connections not always working due to discovery limitations on Android

Running Ping Pong BT example on two Android devices doesn't work (at least not on my setup) due to a few bugs:
Setup :

• Nexus 5x Android 8.1
• HTC 10 Android 8.0
• Install Ping Pong BT Example on both devices, run it as server on Nexus.

The problems:

• the Nexus device lists a few reserved UUIDs and the custom one, but none of these reserved UUIDs is an SPP UUID.
• the HTC device finds the UUID but it doesn't set the QBluetoothUuid::Rfcomm because it doesn't find any SPP UUID first.
• HTC try to use the QBluetoothServiceInfo prvided by the QBluetoothServiceDiscoveryAgentPrivate::populateDiscoveredServices but it fails in QBluetoothSocketPrivateAndroid::connectToService because if (!ensureNativeSocket(service.socketProtocol())) finds only L2capProtocol in the previous service protocols list and it returns an error.

The proposed fixes are:

• as long as the Android provides only a list of UUIDs (without any SDP) we should assume that all custom UUIDs are SPP.
• as long as Android allows only Rfcomm protocols we should set it to all (custom?) UUIDs and to the reserved SPP UUID.