Added test to test vtkSynchronizedRenderers.

Adding test to test use of vtkSynchronizedRenderers in client-server mode. Also
fixed vtkTestDriver to respect exit code from processes so that it catches
errors.

Change-Id: I2cf888bbb3aadf5a534a7e683106bc86cfba984b
Merge topic 'add_client_server_rendering_test' into master

84892990 Added test to test vtkSynchronizedRenderers.