idviews: Enforce objectclass check in idoverride*-del
    
    Even with anchor to sid type checking, it would be still
    possible to delete a user ID override by specifying a group
    raw anchor and vice versa.
    
    This patch introduces a objectclass check in idoverride*-del
    commands to prevent that.
    
    https://fedorahosted.org/freeipa/ticket/5029
    
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>