Fix for polyhedron cells.

This happens for datasets containing a mixture of cell types.  The
vtkIdList was not reset consistently between polyhedron cells and other
cell types.

Change-Id: I2ace508eff3515ac2b6173250d8e2d338e4ba3de
Merge topic 'fix-append-filter-for-polyhedron-cells-rel' into master

ee02727b Fix for polyhedron cells.