Do not add the served by to the header

In our workflow we use a staging server and do a puppet agent -t
--server --noop to see what changed. The served by header changes all
the files and triggers lots of refreshes. This makes it very hard to
spot what changed and what not.
Respect the SSL param in the vhost template

As suggested in https://github.com/theforeman/puppet-foreman/issues/83,
the SSL vhost should not be created when SSL is disabled.