Fix external window stereo mode position for OpenGL2 backend
Fix external window stereo mode position for OpenGL2 backend

sumedhasingla/VTK,mspark93/VTK,SimVascular/VTK,sumedhasingla/VTK,mspark93/VTK,gram526/VTK,keithroe/vtkoptix,sankhesh/VTK,sankhesh/VTK,gram526/VTK,sumedhasingla/VTK,sankhesh/VTK,jmerkow/VTK,keithroe/vtkoptix,candy7393/VTK,jmerkow/VTK,mspark93/VTK,msmolens/VTK,sumedhasingla/VTK,keithroe/vtkoptix,keithroe/vtkoptix,msmolens/VTK,mspark93/VTK,SimVascular/VTK,mspark93/VTK,demarle/VTK,demarle/VTK,msmolens/VTK,candy7393/VTK,gram526/VTK,jmerkow/VTK,SimVascular/VTK,SimVascular/VTK,keithroe/vtkoptix,SimVascular/VTK,keithroe/vtkoptix,msmolens/VTK,candy7393/VTK,gram526/VTK,mspark93/VTK,mspark93/VTK,candy7393/VTK,jmerkow/VTK,sankhesh/VTK,jmerkow/VTK,sankhesh/VTK,candy7393/VTK,jmerkow/VTK,demarle/VTK,mspark93/VTK,candy7393/VTK,gram526/VTK,sumedhasingla/VTK,demarle/VTK,gram526/VTK,demarle/VTK,sumedhasingla/VTK,sumedhasingla/VTK,sankhesh/VTK,keithroe/vtkoptix,SimVascular/VTK,candy7393/VTK,demarle/VTK,jmerkow/VTK,demarle/VTK,sankhesh/VTK,sumedhasingla/VTK,jmerkow/VTK,keithroe/vtkoptix,SimVascular/VTK,SimVascular/VTK,msmolens/VTK,msmolens/VTK,gram526/VTK,gram526/VTK,msmolens/VTK,sankhesh/VTK,msmolens/VTK,demarle/VTK,candy7393/VTK