HAT: turn off mod_php

With this change, hhvm appservers will not use mod_php anywhere and all
php files will be interpreted via HHVM. Subsequent changes will make
direct proxy calls for all the main wiki endpoints, which is more performant.

Change-Id: Ie7c0dc64f7c6268af79b774e8653f5d4da1710d9
Signed-off-by: Giuseppe Lavagetto <glavagetto@wikimedia.org>