Add missing "global" declarations.
  Simplify: there is no need for both a global variable and a lock do just carry a boolean with atomic access.
  Add the possibility to put activity tool back in a working state after process_shutdown has been called.


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@24988 20353a03-c40f-0410-a6d1-a30d3c3de9de