fixes #6330 - using pulp & pulp_node features of smart proxy

* to determine the default smart proxy
* to determine whether to show the lifecycle env selection screen
* to determine which proxies to show under the content source selection on host(group) page

Depends on 
 * [ ] https://github.com/theforeman/smart-proxy-pulp/pull/1
 * [ ] https://github.com/Katello/puppet-capsule/pull/13
 * [ ] https://github.com/Katello/katello-installer/pull/95
If I understand it correctly, the default capsule is the one installed on the sat6, so the consensus was to match it based on the fqdn equality. Also, does the default capsule installed on the sat6 have the pulp feature set? @bbuckingham thoughts?