Changed implementation of proxy setup

Changed the setup_http_proxy method to setup_proxy.
The same arguments are used as before. This change includes
workarounds for pulp proxy configuration. However, until BZ1114083
is fixed, easier proxy support will not be possible.
Just to be clear, you're restarting each service individually because running ``katello-service restart`` won't do it (and thus the ``broken`` on your comment)?