Fixed dead store warning by reformulating loop
Fixed dead store warning by reformulating loop

Switched while to do-while to fix warning about initial 'rayMag' setting
being dead.

Change-Id: I3944988ec87f9c9b51aa1b19a1ee3aaa2ad85b47

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