refs #6145 - calculating installation url based on smart proxy

Opening mainly to abuse jenkens and run tests

Main PR here https://github.com/Katello/katello/pull/4241
I'm not 100% sure what you mean here.  We automatically create the operating system and associate the correct arches to them upon.  If they already exist we just associate the correct arches.  The user may be able to go in and modify the associations, but that is expected (just as they could go in and modify/delete install media and OSs before)

host.arch  seems to be a required field