Note this also fixes TestERP5Type.test_04_CategoryAccessors
A shorter test case would be:

  def test(self):
    self.login()
    self.portal.portal_types.Person.foo = 0
    self.portal.person_module.newContent(portal_type='Person')
    transaction.abort()
    self.portal.portal_types.Person.foo = 0
    self.portal.portal_categories.region.newContent()
    self.portal.person_module.newContent(portal_type='Person')
    transaction.commit() # raise ConflictError without this fix

(provided Person portal type does not have 'type_class' attribute at the
 beginning).

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@41203 20353a03-c40f-0410-a6d1-a30d3c3de9de