Fix health check view

Generated an error when rendering JSON:
AttributeError: 'str' object has no attribute 'identifier'

pount/views.py

@@ -6,11 +6,11 @@ class HealthCheckView(MainView):
     def render_to_response_json(self, plugins, status):
         return JsonResponse(
             {
-                str(p.identifier()): {
+                str(identifier): {
                     "status": "OK" if p.status == 1 else "ERROR",
                     "took": p.time_taken,
                 }
-                for p in plugins
+                for identifier, p in plugins.items()
             },
             status=status,
         )