[CLEANUP] Cleanup code in ext:backend/Configuration

Resolves: #63382
Releases: master
Change-Id: I1f940fefdde2801e8eced5be6ab44e3d9bf326d4
Reviewed-on: http://review.typo3.org/33521
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Frank Nägler <typo3@naegler.net>
Tested-by: Frank Nägler <typo3@naegler.net>
Reviewed-by: Frederic Gaus <gaus@flagbit.de>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>