add activity=SQLQueue parameter to activate method. This permit to execute the activity as many times as they are called. (before, if it was called two time at the same time, only one activity was executed, now two).

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@25547 20353a03-c40f-0410-a6d1-a30d3c3de9de