Don't ignore noaddons commandline opt in game_config_manager

When the unit tests are running, the game_launcher, game_config
code is never involved, so the noaddons cmd line opt cannot be
ignored. This commit makes it so that regardless of game_config
value, the --noaddons command line flag is respected.

This reverts commit 7fd093d7c0bb425756ca3faa01798c67d9bc8cba.