Revert "Fix permissions issue with domain socket"

This reverts commit b16ea176a30b8f82413f8baafd3350a4cfdf64ad.
Fix permissions issue with domain socket

Use root for php-fpm to work around a PHP-specific issue when using nginx/apache to server PHP apps in dokku.

Obtained fix from: https://github.com/Xe/heroku-buildpack-php/commit/1657752f506ce867f01cecdb595c52d5ac4245fc