simulation: Do not perform migration for Handle MultiPropertyEquivalenceTester (quantity).

Followup of: "simulation: improve equivalence testers explanations messages".

product/ERP5/mixin/equivalence_tester.py

@@ -226,8 +226,9 @@ class EquivalenceTesterMixin:
     have on this equivalence tester.
     """
     tested_property = getattr(self, 'tested_property', None)
-    if tested_property != None:
-      if isinstance(tested_property, tuple):
+
+    if (getattr(self, '_baseGetTestedPropertyList', None) is None and
+        isinstance(tested_property, tuple)):
       if len(tested_property) == 1:
         new_value = tested_property[0]
       else:
@@ -242,12 +243,15 @@ class EquivalenceTesterMixin:
     return self._baseGetTestedProperty()
 
   def getTestedPropertyList(self):
+    if getattr(self, '_baseGetTestedPropertyList', None) is None:
       return [self.getTestedProperty()]
 
+    return self._baseGetTestedPropertyList()
+
   def getTestedPropertyTitle(self):
     tested_property_title = getattr(self, 'tested_property_title', None)
-    if tested_property_title != None:
-      if isinstance(tested_property_title, tuple):
+    if (getattr(self, '_baseGetTestedPropertyTitleList', None) is None and
+        isinstance(tested_property_title, tuple)):
       if len(tested_property_title) == 1:
         new_value = tested_property_title[0]
       else:
@@ -262,4 +266,7 @@ class EquivalenceTesterMixin:
     return self._baseGetTestedPropertyTitle()
 
   def getTestedPropertyTitleList(self):
+    if getattr(self, '_baseGetTestedPropertyTitleList', None) is None:
       return [self.getTestedPropertyTitle()]
+
+    return self._baseGetTestedPropertyTitleList()