Executive was setting update extent initialized falsely.

vtkStreamingDemandDrivenPipeline was setting
UPDATE_EXTENT_INITIALIZED when updating the whole extent,
which was causing pipelines not to re-execute when extents
changes. Fixed.

Change-Id: Ic696ba7e8290f29450864b2c079a2686747e26f4
Merge topic 'extent-initialized-fix' into master

8c0040fa Executive was setting update extent initialized falsely.