cloudwatch: global before reading queue

Technically, it isn't necessary to use the global keyword before reading
a global value, only modifying it. However, in this case it leaves a
pretty annoying log line.

util/cloudwatch.py

@@ -12,8 +12,8 @@ def get_queue(app):
   """
   Returns a queue to the CloudWatchSender. If a queue/sender do not exist, creates them.
   """
+  global queue
   if queue is None:
-    global queue
     access_key = app.config.get('QUEUE_METRICS_AWS_ACCESS_KEY')
     secret_key = app.config.get('QUEUE_METRICS_AWS_SECRET_KEY')
     queue = Queue()