Rank-0 window of ```ospMPIMultiDisplays``` with ```rattler.json``` is completely black

[ghost]

When I run ospMPIMultiDisplays with rattler.json, the rank-0 window is completely black. Moving the camera with a mouse seems to work fine. It looks like the camera view on the rank-0 is inverted.

[ghost]

A master, rank-0, window tries to show all the areas covered by other, non-zero ranked, windows. In rattler.json, a rank-0 window is the large display in front (see the above image). Since default camera local position in OSPRay is (0,0,0), for the rank-0, the camera has passed through its image plane. A correct camera position should be something like (0,0,-2).

I will update codes so one can specify camera positions for rank-0 displays.