Change BLACK to TRANSPARENT to fix test

* BLACK = 0xFF000000
* TRANSPARENT = 0x000000

These are not the same thing. We want lights that are off to show up as
transparent, and they do.

Test: atest LightsServiceTest
Bug: 154638739
Change-Id: I6db2bef8c543688ad76577e5aae363f26ef0b1d2