The OpenGL2 backend does not define a vtkOpenGL2ContextDevice2D class,
so this test will not run when built with OpenGL2. Change it to run if
OpenGL2 is enabled as the OpenGL2 backend requires higher than OpenGL
version 2 OR if the OpenGL1 backend is enabled but Open GL version 2
is available.

Added alternate baseline for TestScalarsToColors output to
accommodate minor differences in OpenGL2 backend.