BUG: The vtkCellPicker was not returning image mappers.
BUG: The vtkCellPicker was not returning image mappers.

When vtkImageActor got a mapper (in July 2011), I apparently forgot to
modify vtkCellPicker so that it would return that mapper.  Better late
than never.

Change-Id: I5a3bca3d610c5dab34db4a70430e8ca575297633

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