fix a case of discarded arrays
fix a case of discarded arrays

XDMF can mark any number of arrays as scalars, ids etc.
VTK can only mark one and the way I was doing it was just wrong.
So choose the first (arbitrarily). Another valid choice is none.

Change-Id: Ib9c998035bfd6860ead3d885a934af1a4e7a1b1a

candy7393/VTK,msmolens/VTK,hendradarwin/VTK,sumedhasingla/VTK,gram526/VTK,SimVascular/VTK,jmerkow/VTK,sumedhasingla/VTK,jmerkow/VTK,berendkleinhaneveld/VTK,berendkleinhaneveld/VTK,sumedhasingla/VTK,jmerkow/VTK,candy7393/VTK,sumedhasingla/VTK,msmolens/VTK,sumedhasingla/VTK,candy7393/VTK,berendkleinhaneveld/VTK,keithroe/vtkoptix,johnkit/vtk-dev,msmolens/VTK,sankhesh/VTK,sankhesh/VTK,hendradarwin/VTK,ashray/VTK-EVM,msmolens/VTK,ashray/VTK-EVM,msmolens/VTK,demarle/VTK,candy7393/VTK,sankhesh/VTK,ashray/VTK-EVM,sankhesh/VTK,SimVascular/VTK,mspark93/VTK,ashray/VTK-EVM,johnkit/vtk-dev,demarle/VTK,demarle/VTK,berendkleinhaneveld/VTK,SimVascular/VTK,jmerkow/VTK,keithroe/vtkoptix,msmolens/VTK,msmolens/VTK,candy7393/VTK,SimVascular/VTK,demarle/VTK,demarle/VTK,ashray/VTK-EVM,jmerkow/VTK,ashray/VTK-EVM,hendradarwin/VTK,mspark93/VTK,sankhesh/VTK,demarle/VTK,mspark93/VTK,berendkleinhaneveld/VTK,berendkleinhaneveld/VTK,sankhesh/VTK,gram526/VTK,mspark93/VTK,demarle/VTK,demarle/VTK,hendradarwin/VTK,jmerkow/VTK,msmolens/VTK,gram526/VTK,sumedhasingla/VTK,ashray/VTK-EVM,sumedhasingla/VTK,johnkit/vtk-dev,jmerkow/VTK,keithroe/vtkoptix,jmerkow/VTK,candy7393/VTK,johnkit/vtk-dev,johnkit/vtk-dev,candy7393/VTK,SimVascular/VTK,SimVascular/VTK,sankhesh/VTK,hendradarwin/VTK,gram526/VTK,SimVascular/VTK,berendkleinhaneveld/VTK,keithroe/vtkoptix,keithroe/vtkoptix,mspark93/VTK,sumedhasingla/VTK,keithroe/vtkoptix,gram526/VTK,mspark93/VTK,johnkit/vtk-dev,ashray/VTK-EVM,hendradarwin/VTK,SimVascular/VTK,mspark93/VTK,gram526/VTK,candy7393/VTK,hendradarwin/VTK,gram526/VTK,sankhesh/VTK,mspark93/VTK,keithroe/vtkoptix,gram526/VTK,keithroe/vtkoptix,johnkit/vtk-dev