fix rejected pin value of -1 from init

[cebtenzzre]

Use None consistently as the placeholder for the pin value, and never -1, as validate_pin rejects -1 with an exception and can be called before the thread's pin is set:

listen_state(callback, entity)  # no pin_thread specified
    → determine_thread(name, None, None)
    → pin_thread = objects[name].pin_thread  # gets -1
    → validate_pin(name, -1)
    → -1 < 0 is True
    → raise PinOutofRange  💥

Fixes #2343