Adds settings.cfg for gce-backend.

appengine/gce-backend/main.py

 # Copyright 2015 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 """Handlers for HTTP requests."""
 
 from components import utils
 
 import gae_ts_mon
 
+import config
 import handlers_cron
 import handlers_endpoints
 import handlers_queues
 
 
+def is_enabled_callback():
+  return config.settings().enable_ts_monitoring
+
+
 def main():
   utils.set_task_queue_module('default')
   apps = (
     handlers_endpoints.create_endpoints_app(),
     handlers_cron.create_cron_app(),
     handlers_queues.create_queues_app(),
   )
   for app in apps[1:]:
     # Not callable on endpoints app
-    gae_ts_mon.initialize(app=app)
+    gae_ts_mon.initialize(app=app, is_enabled_fn=is_enabled_callback)
   return apps
 
 
 endpoints_app, cron_app, queues_app = main()