Implement Notification.DEFAULT_LIGHTS flag.

This flag was already in the public API but did not do anything until now.
We now use it so we can override the default notification LED color on a per device basis.

Change-Id: I0d6e239b7da2fdbeda9608d6d4de3e778aa88e2c
BUG: 2329568

Signed-off-by: Mike Lockwood <lockwood@android.com>