scalability_test: fixing missing parameter

scalability_test/__init__.py

@@ -33,7 +33,7 @@ class WendelinERP5_scalability():
                                     instance_information_dict['zope-address'])
     return metrics_url + "/ERP5Site_getScalabilityTestMetric"
 
-  def getScalabilityTestOutput(metric_list):
+  def getScalabilityTestOutput(self, metric_list):
     if not metric_list: return None
     output_json = json.loads(metric_list[0])
     for metric in metric_list: