Black png returned when using a vnc session

[durack1]

@danlipsa @doutriaux1 I just ran the demo script BlueMarble_huss_satellite_view.html and received the appropriate graphic on the active VNC screen. What was saved to the png is below, and is certainly not what I was expecting: This is certainly not the expected behavior. What additional information do you require to better replicate the issue:

In [1]: import cdat_info
In [2]: cdat_info.version()
Out[2]: ['', 'v2.8']