Ticket #47731 - A tombstone entry is deleted by ldapdelete
    
    Description: A tombstone deletion by ldapdelete op from client is
    supposed to fail.  The failure from SLAPI_PLUGIN_BETXNPOSTOPERATION
    was ignored in 389-ds-base-1.2.11 plugin_call_func and it was not
    passed to the backend to abort.  This patch added the check in the
    same way as in 389-ds-base-1.3.1 and newer.
    
    https://fedorahosted.org/389/ticket/47731
    
    Reviewed by rmeggins@redhat.com (Thank you, Rich!)