Settings might get overwritten by server.cfg in the first map

Game settings placed in server.cfg might override whatever configuration ReDM sets within the gamemode, at least for the first map, this is due the configuration is being loaded in plugin_cfg(), at least until the map is changed. This is a minor issue but very annoying.

Changing `plugin_cfg()` to `OnConfigsExecuted()` in the plugin's source code fixes this issue. 