change the way we shut down the R interface
change the way we shut down the R interface

The use of atexit() was causing R code that uses the parallel
library to fail nondeterministically.

Change-Id: Iff8eaafd786341f7bc10d50338c50525be492385

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