idviews: Restrict anchor to name and name to anchor conversions
When converting the ID override anchor from AD SID representation to
the object name, we need to properly restrict the type of the object
that is being resolved.
The same restriction applies for the opposite direction, when
converting the object name to it's SID.
https://fedorahosted.org/freeipa/ticket/5029
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>