Backup Config files before updating so the box can be reconfigured

Before apache couldn't be reconfigured as the config files were overwritten.

https://trello.com/c/Ynhqi1eq/3143-p0-if-i-deploy-a-php-box-in-google-compute-i-can-access-the-directory-with-all-the-installation-files-and-apache-configuration-f

@arnaud @alberto