Ticket #47692 single valued attribute replicated ADD does not work
    
    https://fedorahosted.org/389/ticket/47692
    Reviewed by: nhosoi,lkrispenz (Thanks!)
    Branch: master
    Fix Description: Add special corner case handling for the case where
    - attr is deleted with vdcsn and adcsn CSN1
    - attr vucsn is NULL
    - incoming mod/add has CSN2 where CSN2 > CSN1
    in this case, just keep the new mod/add value as the present value.
    Platforms tested: RHEL6 x86_64
    Flag Day: no
    Doc impact: no