Fix small bug when loading package config files

I think there is a small bug um "mako_cascading_paths" when loading config files in a package.

The generated paths are:

-> app/config/packages/foobar/config_file.php
-> app/foobar/config/config_file.php

Looks like the function is generating the right path to load file in app/config tree but is generating wrong path to app/package tree.