[BUGFIX] Asset update does not refresh thumbnail

Early update time stamp of processed image. This is needed for
the browser to get a new version of the thumbnail.

Change-Id: I3d9390517088a13126b3955adb742fa2528bd86d
Releases: 2.0.0
Resolves: #53306
Reviewed-on: https://review.typo3.org/25151
Reviewed-by: Fabien Udriot
Tested-by: Fabien Udriot