Undefine attribute methods on all descendants when resetting column info

If we don't do this, then we end up with an inconsistent situation where
a parent class may e.g. reset column information, but child classes will
contine to see attribute methods as already generated, and thus not pick
up this new column (falling through to method_missing).

activerecord/lib/active_record/model_schema.rb

@@ -425,7 +425,7 @@ module ActiveRecord
       #  end
       def reset_column_information
         connection.clear_cache!
-        undefine_attribute_methods
+        ([self] + descendants).each(&:undefine_attribute_methods)
         connection.schema_cache.clear_data_source_cache!(table_name)
 
         reload_schema_from_cache