BUG: 14771: Fix Annotate Data filter in parallel.

vtkAnnotateGlobalDataFilter failed in parallel due to several reasons:

1. annotation.py was imported client-side modules which failed when
running on pvserver. Fixed that.
2. vtkPythonAnnotationFilter was changing its MTime in RequesData. Fixed
that.

Change-Id: I59dcab2e4c4e0ceff7e2c5315b579ec1baadd5e4
Merge topic '14771_fix_global_annotation_filter' into next

b4a19dca BUG: 14771: Fix Annotate Data filter in parallel.