include @items in OTA restore to enable progress bar on mobile

```xml
<OpenRosaResponse items="12" xmlns="http://openrosa.org/http/response">
    <message nature="ota_restore_success">Successfully restored account user1!</message>
    <Sync xmlns="http://commcarehq.org/sync">
        <restore_id>e14c3bd4bbf68c98e7ca1a4d8fd5b4d6</restore_id>
    </Sync>
    <Registration xmlns="http://openrosa.org/user/registration">
        ...
```