idoverride: Ignore ValidationErrors when converting the anchor
    
    When converting the anchor to a human readable form, SID validation
    may fail, i.e. if the domain is no longer trusted.
    
    Ignore such cases and pass along the anchor in the raw format.
    
    https://fedorahosted.org/freeipa/ticket/5322
    
    Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>