[UPower Backend] Check for Bluez for any unknown battery type
Instead of only doing it explicitly for UP_DEVICE_KIND_UNKNOWN
we'll check it for any battery that we did not handle, so that
we at least know it's a Bluetooth battery should UPower gain
additional device types in the future, as has happened before.
@nicolasfella 's headset should now show up as a Bluetooth battery at least (Future we might want to extend the battery types we support in Solid)