rb-site: Deploy correct Apache 2.4 authorization

Apache 2.4 uses a different authorization config than 2.2. This change adds
some smarts to rb-site to detect when using Apache 2.4 and use "Require all
granted" instead of "Allow from all".

Testing Done:
Applied the patch and deployed it on a system with Apache 2.4.2. It properly
detected the version and put "Require all granted" into the apache-wsgi.conf

Bugs closed: 3210

Reviewed at https://reviews.reviewboard.org/r/5338/