Fix redirection from non-ssl to ssl when using HA (bnc#907044)

Two things were broken:

 - without the VirtualHost for non-ssl port, the rewrite was not working
   when a request was coming from haproxy as the requested port was
   really 80, not 5580 (and we had a RewriteCond filtering this out).
   Now VirtualHost is the way we restrict the rewrite rules to the
   requests we care about.

 - we shouldn't redirect to port 5581 for requests coming through
   haproxy because 5581 is not visible from the outside. So what we do
   is that we only redirect to an explicit port for ssl when the
   explicit port for non-ssl is the one we listen on. Otherwise, we just
   redirect to the host.

https://bugzilla.suse.com/show_bug.cgi?id=907044
Merge pull request #193 from vuntz/ha-fix-ssl-redirect

Fix redirection from non-ssl to ssl when using HA (bnc#907044)