Valid core config options aren't cached to be retrieved using `GetCoreConfigValue` after they've been loaded from core.cfg or set through the `sm config` root console menu.
E.g. `sm config ServerLang` would return `[SM] No such config option "ServerLang" exists.` all the time.
Stop notifying other listeners if the config key was consumed, but don't skip adding it to the cache.
Also fix `FollowCSGOServerGuidelines` always showing as unhandled command when being changed through `sm config FollowCSGOServerGuidelines yes`.