queue.yamlにリトライ制限を記述

queue.yamlにretry_parametersを追加する。

Retrying Tasks in Push Queues

In fooqueue, tasks are retried at least seven times and for up to two days from the first execution attempt. After both limits are passed, it fails permanently.

http://code.google.com/intl/ja/appengine/docs/python/config/queue.html#Setting_the_Storage_Limit_for_All_Queues

queue:
- name: fooqueue
  rate: 1/s
  retry_parameters:
    task_retry_limit: 7
    task_age_limit: 2d