Fix NameError.

Traceback (most recent call last):
  File "apachedex/__init__.py", line 1274, in wrapper
    return func(*args, **kw)
  File "apachedex/__init__.py", line 1586, in main
    site_data.rescale(rescale, getDuration)
  File "apachedex/__init__.py", line 605, in rescale
    for value_date, data in getattr(self, attribute_id).iteritems():
NameError: global name 'attribute_id' is not defined

apachedex/__init__.py

@@ -602,7 +602,7 @@ class ERP5SiteStats(GenericSiteStats):
       self.no_module[id_] = new_date_dict
 
     attribute = defaultdict(partial(APDEXStats, threshold, getDuration))
-    for value_date, data in getattr(self, attribute_id).iteritems():
+    for value_date, data in self.site_search.iteritems():
       attribute[convert(value_date)].accumulateFrom(data)
     self.site_search = attribute