[BUGFIX] Failing unit test in tslib_adminPanelTest

The change from issue #28639 did not refactor the
according unit test which is done now.

Change-Id: I6c7d8389901a7ca867b354a2081af7beb8c2ddc0
Resolves: #28970
Reviewed-on: http://review.typo3.org/4314
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn