Ticket 47771 - Move parentsdn initialization to avoid crash
    
        Bug Description:  It's possible to call slapi_sdn_done() before parentsdn is
                          initialized - which will crash the server.
    
        Fix Description:  Initialize parentsdn at the top of the function.
    
        https://fedorahosted.org/389/ticket/47771
    
        Reviewed by: nhosoi(Thanks!)