[BUGFIX] Fix current storage computing for non admin User

Change-Id: I5e51686b2cc7028755bb1add6b2305b6361ac1ae
Releases: 3.2
Resolves: #62269
Reviewed-on: http://review.typo3.org/33329
Reviewed-by: Fabien Udriot <fabien.udriot@ecodev.ch>
Tested-by: Fabien Udriot <fabien.udriot@ecodev.ch>