Post building script shall work in all possible cases.

Catching only WorkflowException was in consistent:

 * user without privileges in accounting was able to build invoice coming from
   packing list without price currency (script worked well)
 * user with privileges in accounting, which delivered packing list, was not
   able to confirm this invoice, as ValidationFailed was raised


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@31889 20353a03-c40f-0410-a6d1-a30d3c3de9de