Ticket #47424 - Replication problem with add-delete requests on single-valued attributes
    
    https://fedorahosted.org/389/ticket/47424
    Reviewed by: lkrispenz (Thanks!)
    Branch: 389-ds-base-1.2.11
    Fix Description: Change the single master resolve attr code to handle the
    specific case of doing
    add: newvalue
    delete: oldvalue
    Had to add a new API function - csn_compare_ext - to be able to compare CSNs
    without the subsequence number.
    Platforms tested: RHEL6 x86_64
    Flag Day: no
    Doc impact: no
    (cherry picked from commit bf53a29af973648c520b005ad37f7a83db4b905b)