Config update for allowed log sources

Completely resets the allowed log sources from scratch.

Also:
- renamed initLogSourceWhitelist to initAllowedLogSources.
- refactored tests to have cleaner asserts on data structures

Test: atest statsd_test
Bug: 162323471
Change-Id: Ie717da732eea82c764b5b1f272080a4d97a7a8eb