Fixes #5503/BZ1102315 - restrict UI interactions to actual permissions.

http://projects.theforeman.org/issues/5503
https://bugzilla.redhat.com/show_bug.cgi?id=1102315
@ehelms  not sure I get this
2 different checks happening -> 
1) Checks whether you have the ablility to promote a content view
2) Other is more context sensitive.. It checks to see whether you have promotable permissions on any environment. 
I don't like duplicating logic like this in 2 places. So model seems like the right place imo.