This enforces using english locale before running facter commands.

This fix problems related to command output parsing on platforms that are not using English Locale. 

In facter we was enforcing the LANG=C, but that has lower priority than LC_ALL. 
(http://www.gnu.org/software/gettext/manual/html_node/Locale-Environment-Variables.html) 

This commit configure facter to export the LC_ALL var instead of LANG. 

(I could not add that merge in the currently Open Pull Request: https://github.com/puppetlabs/facter/pull/476, )