Move User#role_allows? logic in to RBAC
Move User#role_allows? logic in to RBAC

We had to put the 'nil feature logic' back to the controller layer as
that front end concern appears to be incompatible with the model code.
(transferred from ManageIQ/manageiq@ce56a12d61e39f7fa14ba4686e9b8f97351c128f)

ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic