title: redis keys not being expired
body: <pre><code>irb(main):001:0&gt;  redis_key = User.create_prev_order_in_progress_redis_key(194652)
      =&gt; "prev_order_in_progress_194652"
  irb(main):002:0&gt; $redis_secondary.get(redis_key)
      =&gt; "1"
  irb(main):003:0&gt; $redis_secondary.ttl(redis_key)
      =&gt; 0
  </code></pre>
  
  <p>I have moved my <code>redis</code> server to a new server so that's probably why
  But I have no idea why these keys are not nil even though the <em>ttl</em> is 0.</p>
  
  <p><code>redis</code> version is 2.8.3</p>