For some reason this is needed using openni

This is just a workaround, the real problem is that the default values expect depth_registered stuff:
```
[ INFO] [1395248076.002277778]: Subscribed to topic:/camera/rgb/camera_info with queue size of 1
[ INFO] [1395248076.003073369]: Subscribed to topic:/camera/rgb/image_raw with queue size of 1
[ INFO] [1395248076.003968179]: Subscribed to topic:/camera/depth_registered/camera_info with queue size of 1
[ INFO] [1395248076.004994459]: Subscribed to topic:/camera/depth_registered/image_raw with queue size of 1
```

Using openni2 this is not a problem as it's published by default but using openni those are not published, so this workarounds that.