idviews: Handle Default Trust View properly in the framework
Make sure that:
1.) IPA users cannot be added to the Default Trust View
2.) Default Trust View cannot be deleted or renamed
Part of: https://fedorahosted.org/freeipa/ticket/3979
Reviewed-By: Petr Viktorin <pviktori@redhat.com>
Reviewed-By: Petr Vobornik <pvoborni@redhat.com>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>