title: rpush not delivery message in rpush.log
body: <p>I am using rpush gem to send push message to iphones. One user complain message sometime delivered some times not. I checked the rpush.log. Out of 10 messages, 3 got delivered and received by the phone as shown in rpush.log:
      [2015-05-25 22:25:45] [xxxx_production] 48121 sent to 083a15xxx
      [2015-05-25 22:27:57] [xxx_production] 48124 sent to 083a15xxx
      [2015-05-25 22:29:24] [xxx_production] 48125 sent to 083a15xxx</p>
  
  <p>Other not delivered messages dont show up in rpush.log. But they show in rpush_notifications table as delivered=1
  and failed=0. Such as:</p>
  
  <pre><code>| id    | delivered | delivered_at        | failed | failed_at |
  | 48122 |         1 | 2015-05-25 22:26:47 |      0 | NULL 
  </code></pre>
  
  <p>I don't know how to further debug the problem? What may cause rpush not deliver the message but still update the rpush_notifications table as delivered=1?</p>