Ticket 48907 - register-ds-admin fails to find local config DS
    
    Bug Description:  If adm.conf's startLdap directive uses the server instance ID
                      without the prefix "slapd-" then the registeration script
                      keeps asking for an admin password and never progresses.
    
    Fix Description:  Allow getLocalConfigDS() to handle instacne names with/without
                      the "slapd-" prefix.
    
    https://fedorahosted.org/389/ticket/48907
    
    Reviewed by: nhosoi(Thanks!)