Revert "mark file uploading tests as expected failure." as these Functional Tests are not supposed to fail.

This reverts commit ade16831.

enablePrivilege, and thus UniversalFileRead used to upload files, was disabled
in Firefox 17. Since SlapOS Firefox has been upgraded, "The operation is insecure"
error is raised when uploading files. However, this doesn't mean that these tests
should be expected to fail (and if they are, they should be removed instead).