[BUGFIX] Wrong directory path checked while unzipping extension

Uploading an extension a zip file has a wrong check for directory
existence. Fix the path to this directory in the check.

Resolves: #65702
Releases: master,6.2
Change-Id: I61b46a6f9efb55e3f8b6843597a31b458752fc46
Reviewed-on: http://review.typo3.org/41096


Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Helmut Hummel <helmut.hummel@typo3.org>
Tested-by: Helmut Hummel <helmut.hummel@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>