Add failing test for DDC-2785

Add a failing test for

http://www.doctrine-project.org/jira/browse/DDC-2785
The `$oid` is still in `$this->entityStates`, and also in `$this->entityIdentifiers`, but with a different `phonenumber`:

```php
// added to the beginning of getEntityState()
foreach ($this->entityIdentifiers as $oid => $id_array)
{
    if ($oid === spl_object_hash($entity))
    {
          var_dump($id_array['phonenumber'], $entity->phonenumber);
     }
}
```

Output:
```
string(13) "53c3d198133c2"
string(13) "53c3d1981570a"
```

Not sure how I would go about finding the same object (as in the same phonenumber). Do you suspect any particular place where it might be?