Revert "[TASK] Remove usage of property $new_unique_uid"

This reverts commit cf2eb86c799b652d64ea6858dd2715444e232c0b.

The removed code is not dead and should not be removed
without detailed investigation.

Change-Id: I4291a6ff4b06b74fb9fb5e757fc738f8bd413ca5
Reviewed-on: http://review.typo3.org/35393
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>