mpi4py: use old code with Python 2.6 as well
mpi4py: use old code with Python 2.6 as well

Seems to have issues on OS X despite it working with 2.7 and the symbol
being in both.

Change-Id: If0d8e8f98491e6b024c9794b260a8545b8a8d554

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