[FIX] registry: recompute `pure_function_fields` after every setup

The lazy property `pure_function_fields` was not invalidated upon every setup
of models, and hence could contain old instances of fields.  As every model
setup re-creates instances of fields, the property has to be recomputed.

openerp/modules/registry.py

@@ -173,6 +173,8 @@ class Registry(Mapping):
 
             :param partial: ``True`` if all models have not been loaded yet.
         """
+        lazy_property.reset_all(self)
+
         # load custom models
         ir_model = self['ir.model']
         cr.execute('select model from ir_model where state=%s', ('manual',))