Trac Ticket #437 - variable dn should not be used in ldbm_back_delete
    
    https://fedorahosted.org/389/ticket/437
    
    Fix description: When SLAPI_DELETE_TARGET_DN was replaced with
    SLAPI_DELETE_TARGET_SDN, removing obsolete variable dn was
    incomplete.  Actually, the variable dn is still referred in
    some error messages.  This patch sets the value from Slapi_DN
    to the dn variable.
    (cherry picked from commit b37e0c2e878ecef8c46449ce4e44a3c0deb344f2)