BUG #15093: Fixed issue with stereo rendering.

The problem was that the StereoType set on vtkRenderWindow was
incorrect. It ended up picking Crystal Eyes incorrectly. The problem was
due to the the "StereoType" property being reset to default by
vtkSMParaViewPipelineController. This fixes that.

Also added tests to test setting of stereo modes to catch this in
future.

Change-Id: I20d7227d2059be007b8ff2d1a6abffa349679345
Merge topic '15093_fix_stereo_issues' into next

0c9dfba0 BUG #15093: Fixed issue with stereo rendering.