set self.tracer to None (#18)

This change is for APIs built using the older AI for Earth API framework

APIs/1.0/base-py/ai4e_service.py

@@ -52,6 +52,8 @@ class APIService():
 
         if not isinstance(self.log, AI4EAppInsights):
             self.tracer = self.log.tracer
+        else:
+            self.tracer = None
 
         self.api_task_manager = TaskManager()
         signal.signal(signal.SIGINT, self.initialize_term)
@@ -210,4 +212,4 @@ class APIService():
             self._log_and_fail_exeception(is_async, **kwargs)
             abort(500)
         finally:
-            self.decrement_requests(api_path)
+            self.decrement_requests(api_path)