fix changetask DB scheme


git-svn-id: https://forge.indepnet.net/svn/glpi/trunk@23014 35612d4c-9d10-0410-837c-bf9dd1be60d7
more DB scheme fix for tasks


git-svn-id: https://forge.indepnet.net/svn/glpi/trunk@23015 35612d4c-9d10-0410-837c-bf9dd1be60d7