- getProductLine on a Sale Order Line returns nothing
  even if there is a resource defined on the Sale Order
  Line and a product line on this resource (and base
  categories looks like to be well configured)
- portal_type variable is already used in the method
  _getSingleCategoryAcquiredMembershipList, so
  doing "for portal_type in portal_type_list" makes giving any
  random value to the portal type variable
- the portal_type variable can have duplicated portal types,
  in such case the following piece of code always return [],
  so duplicated needs to be removed :
       for portal_type in portal_type_list:
         key = (uid, base_category, portal_type)
         if key in _acquired_object_set:
           return []
         _acquired_object_set.add(key)

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@38053 20353a03-c40f-0410-a6d1-a30d3c3de9de