[TASK] Remove usage of property $new_unique_uid

The property $this->new_unique_uid in PageLayoutController
is never used. Some very strange and dead code can be
just removed.

Resolves: #49608
Releases: master
Change-Id: If4857d412baf21942d5c5a650922dfc8668689ee
Reviewed-on: http://review.typo3.org/21818
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>