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

http://projects.theforeman.org/issues/5503
https://bugzilla.redhat.com/show_bug.cgi?id=1102315
Thoughts on another function to encompass the negative behavior? Seems like that could be easier to differentiate and prevent accidentally missing or forgetting the `!` especially when reading through this.