camera does not work with Asus Nexus 7

```
What steps will reproduce the problem?
1. Start video call between two devices: Asus Nexus 7 (it has only front
camera) and device.
2. You will see on second device that there is no video from the Asus Nexus 7.

What is the expected output? What do you see instead?
Expected output is video from Nexus.

What version of the product are you using? On what operating system?
Ngn stack 2.0 for android.

Please provide any additional information below.

The main problem with Asus Nexus 7 is that it has only one front camera. When
you open the camera on Nexus 7, you should use Camera.open( 0 ) //with
parameter.

So, to fix this issue, you should make the following change in the
NgnCameraProducer class, openFrontFacingCamera function:
camera = Camera.open();
if (camera != null) { //added line
Camera.Parameters parameters = camera.getParameters();
parameters.set("camera-id", 2);
camera.setParameters(parameters);
}
else { //added line
camera = Camera.open(0); //added line
} //added line

```

Original issue reported on code.google.com by `nadk...@gmail.com` on 4 Sep 2013 at 7:18

Start in NgnCameraProducer.openFrontFacingCamera and reproduce the video call described between an Asus Nexus 7 and another device. Check the camera-opening behavior on the front-camera-only Nexus 7, then verify that the peer receives video from the Nexus 7.

Written by the indexing model from the issue text.