Ticket 49241 - Update man page and usage for db2bak.pl
    
    Description:  The usage and man page should state thtthe backup directory
                  is actually a symlink to the the server's backup directory.
                  Otherwise it is misleading, and could eventaully lead to
                  diskspace issues.
    
    https://pagure.io/389-ds-base/issue/49241
    
    Reviewed by: firstyear(Thanks!)
    
    (cherry picked from commit 0804c43991fa29ef7bd946b3e5a37844e2b87da4)