[BUGFIX] Make sure fixPermissions gets 4 digit string

The global file options "fileCreateMask" and "folderCreateMask" should 
always have 4 digits when calling GeneralUtility::fixPermissions() to 
avoid any problems when having a misconfiguration.

Resolves: #36167
Releases: master
Change-Id: I4ad8a98770a63abe7f8ba3de00b0394d211d5d03
Reviewed-on: https://review.typo3.org/44430


Reviewed-by: Michael Oehlhof <typo3@oehlhof.de>
Tested-by: Michael Oehlhof <typo3@oehlhof.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>