[BUGFIX] Check folder permission for default upload folder

The default upload folder has to be writable to add new files.
Do not return a default folder if the user does not have add permissions for it.

Releases: master, 6.2
Resolves: #59589
Change-Id: Iacb7fa8b9b9bdbcb6788485f12f1db00d42b34ae
Reviewed-on: http://review.typo3.org/37481


Reviewed-by: Helmut Hummel <helmut.hummel@typo3.org>
Tested-by: Helmut Hummel <helmut.hummel@typo3.org>
Reviewed-by: Nicole Cordes <typo3@cordes.co>
Tested-by: Nicole Cordes <typo3@cordes.co>
Reviewed-by: Jan Helke <typo3@helke.de>
Reviewed-by: Frans Saris <franssaris@gmail.com>
Tested-by: Markus Klein <klein.t3@reelworx.at>