Fix a bug in Lutron RadioRA2 Scene support

[cdheiser]

Description:

The main lutron component was not properly passing the keypad name to the scene component, resulting in a stack trace like so:

Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/homeassistant/helpers/entity_platform.py", line 128, in _async_setup_platform
    SLOW_SETUP_MAX_WAIT, loop=hass.loop)
  File "/usr/local/lib/python3.6/asyncio/tasks.py", line 358, in wait_for
    return fut.result()
  File "/usr/local/lib/python3.6/concurrent/futures/thread.py", line 56, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/usr/local/lib/python3.6/site-packages/homeassistant/components/scene/lutron.py", line 22, in setup_platform
    (area_name, keypad_name, device, led) = scene_data
ValueError: not enough values to unpack (expected 4, got 3)

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.