Ticket 49070 - ldif2db.pl/db2ldif.pl/db2index.pl displays the wrong usage
    
    Bug Description:  The usage displays "-n instance", but this is misleading as
                      it's supposed to be the backend name.
    
    Fix Description:  Change the usage to use "backend".
    
    https://fedorahosted.org/389/ticket/49070
    
    Reviewed by: nhosoi(Thanks!)