Fix assertion failure when retrying to migrate a workflow history

When a first migration was reverted for any reason (e.g. ConflictError),
the assertion failed because __setstate__ was not called yet to fix the
class back to the old one.

bt5/erp5_core_test/TestTemplateItem/portal_components/test.erp5.testWorkflowHistoryList.py

@@ -173,6 +173,8 @@ class TestWorkflowHistoryList(TestCase):
     self.checkClass(whl, WorkflowHistoryList)
     self.abort()
 
+    self.assertEqual(len(whl), COUNT)
+    self.abort()
     self.checkClass(whl, LegacyWorkflowHistoryList)
     self.assertEqual(len(whl), COUNT)
     self.checkClass(whl, WorkflowHistoryList)

product/ERP5Type/patches/WorkflowTool.py

@@ -759,6 +759,7 @@ class WorkflowHistoryList(NewWorkflowHistoryList):
     stack = [self]
     while True:
       stack.append(bucket)
+      bucket._p_activate()
       assert bucket.__class__ is WorkflowHistoryList, bucket.__class__
       bucket.__class__ = NewWorkflowHistoryList
       bucket = bucket._prev