[BUGFIX] Fix install tool image test path

The temppath for gdlib and combineImages is different
then all other image tests
The assets/images path is set in imageMagickConvert
for other image tests

Releases: master
Resolves: #77851
Change-Id: I4fec0422595045cfb5ca67a48f8e6dae79fc08d7
Reviewed-on: https://review.typo3.org/49864


Reviewed-by: Gleb Levitin <gleb.levitin@dkd.de>
Reviewed-by: Manuel Glauser <mail@manuelglauser.ch>
Tested-by: Manuel Glauser <mail@manuelglauser.ch>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>