Fixes for new/edit widget action
Fixes for new/edit widget action

New:
  - refuse no checked items in Visibility section when user chooses 'By Role'
    and display error flash msg
Edit:
  - fix loading of the Roles

https://bugzilla.redhat.com/show_bug.cgi?id=1209945
(transferred from ManageIQ/manageiq@a4c717f02a3a286caac115abf4b0b596e215748f)

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