Ticket #47692 single valued attribute replicated ADD does not work
    
    https://fedorahosted.org/389/ticket/47692
    Reviewed by: nhosoi,lkrispenz (Thanks!)
    Branch: 389-ds-base-1.2.11
    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
    (cherry picked from commit 59941ea23b6f288617ba1e6ce58238fa59266c9f)
    (cherry picked from commit 01a112121e80505021d0a18afa899b5c46180797)
    (cherry picked from commit a4a46424d59a189552c1d17eed1d52218f3a95b8)
    (cherry picked from commit dad08c10826896dc4e8772ec400d60e3eb0ebbb6)