Synchronize user preferred language with config default language when user changed config.

Current Bug is :
In multilingual when user do change default language from localization setting form, it is not get set properly and config get load w/ previous language.

Proposed solutions :
lets keep user language up to date w/ config default language when user change config from localization settings form.

So when we do load config we could find proper lcMessages from civicrm_uf_match table.