Revert "[BUGFIX] LocalDriver needs to respect "is_writeable""

This change broke the tests

This reverts commit e9543738e14e235087d303abeb1492cf0c8e5f01

Change-Id: I6638ca1c82482bd1b9477fb343b7d566e8fe559c
Reviewed-on: https://review.typo3.org/17498
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel