[BUGFIX] Allow creation of nested folders with same name

Due to a faulty check it was disallowed to create a folder
with the same name as the parent folder.

Resolves: #71253
Releases: master
Change-Id: Iecf1f17534958f10363538dc74612e9a52435a0d
Reviewed-on: https://review.typo3.org/44485


Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>