Remove non-SSL rewrite example from apache::vhost

As apache::vhosts requires $docroot to be set, this example doesn't work. However the non-SSL to SSL rewrite is a very common use case (and setting $docroot to /dev/null doesn't work either). Parameter $docroot should be optional. Or at least it should be possible to skip docroot management (create dir, set owner etc.) for example by setting $manage_docroot = false.