BUG #13782. Fixed vtkTextSourceRepresentation in client-server mode.

vtkTextSourceRepresentation wasn't updating in client-server mode. The problem
was that the client-side representation never realized that the input pipeline
had changed and hence it never delivered new data. This fixes that issue.

Change-Id: Ica53fc3bf3d7100f17d170c150dd9766aac67e0d
Merge topic '13782_fix_text_source' into next

937f0e1 BUG #13782. Fixed vtkTextSourceRepresentation in client-server mode.