Implement HA support through haproxy
Be stronger than apache2 cookbook and enforce the ports we want to use

The apache2 cookbook is kind of broken in how it defines ports to use in
config files, so we need to override this behavior.
Configure horizon to use memcached from all nodes in the cluster
Fix to work when keystone is behind haproxy
Use get_instance helper
HA: also make haproxy listen on port 80 for redirecting to https
We don't use Opscode::OpenSSL::Password anymore