[vtkusers] SetInputArrayToProcess update problems

[Dominik Szczerba]

I have noticed that calling:

threshold->SetInputArrayToProcess(0,0,0,0,scalarName.c_str());

causes the pipeline to update even if scalarName has not changed its
value. On the contrary:

threshold->ThresholdBetween(s1,s2);

does not update (as expected) if s1/s2 have not changed their values.

Is this an expected behavior?

-- Dominik