support apache 2.4 access control syntax

This change allows the stash and apache2 cookbooks to work on Ubuntu 14.04 and Apache 2.4 (default). 

Until the v2.4 changes are merged on the apache2 side, the COOK-3900 branch of the apache2 cookbook must be used, and the node["apache"]["version"] attribute must be set to "2.4". 

Without this change, the Apache proxy will return a 403 error for all requests including the root and /setup