ERP5Type: use constraints accessors in _filteredConstraintList

Constraints are supposed to have a getReference and getConstraintType
methods.

product/ERP5Type/Base.py

@@ -2669,13 +2669,13 @@ class Base( CopyContainer,
         reference_list = filt.get('reference', None)
         if not isinstance(reference_list, (list, tuple)):
           reference_list = [reference_list]
-        constraints = filter(lambda x:x.getProperty('reference') in \
+        constraints = filter(lambda x:x.getReference() in \
             reference_list, constraints)
       if 'constraint_type' in filt:
         constraint_type_list = filt.get('constraint_type', None)
         if not isinstance(constraint_type_list, (list, tuple)):
           constraint_type_list = [constraint_type_list]
-        constraints = filter(lambda x:x.__of__(self).getProperty('constraint_type') in \
+        constraints = filter(lambda x:x.__of__(self).getConstraintType() in \
                 constraint_type_list, constraints)
 
     return constraints