[Bluetooth] Update class of device value whenever possible

The class of device value can only be retrieved via inquiry or during
an incoming connection request. Outgoing connections can't ask for the
class of device. To compensate for this the value is stored and copied
via the inquiry cache, but currently only updated via inquiry. This
update should also happen during an incoming connection request.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>