optimize SSL terminated apache configuration

[James Page]

When SSL termination is enabled, the charm configures separate vhosts for SSL and the actual openstack WSGI backend application, proxying between the two vhosts.

This creates a larger burden on the server and apache in terms of open sockets and worker processes; lets optimize the apache configuration to bake the SSL termination directly into the backend WSGI application vhosts, rather than having separate SSL vhosts + mod_proxy back to the WSGI vhost.