Release the depth filter for better performance

[tfoote]

From this thread: https://3dclub.orbbec3d.com/t/astra-openni2-under-arm-platform-raspberry-pi-2-ubuntu-14-04/282/2 there's an unreleased filter that's not in the github sources. Without that the open source driver does not perform as well.

This was first reported on the ROS review thread at http://discourse.ros.org/t/new-depth-sensor-orbbec-astra-call-for-testing/252/4