[BUGFIX] fixPermissions() on install tool test image

One of the environment image tests misses an explicit
fixPermissions() call on a created image resulting in
potentially broken file permissions on that file.

Change-Id: Ib7e9da2269aaabdd9cc815d8ff2f0d3841b45444
Resolves: #83549
Releases: master
Reviewed-on: https://review.typo3.org/55342


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Tested-by: Jigal van Hemert <jigal.van.hemert@typo3.org>