The latest Qt 5.10 beta includes [1] which breaks KIO all over the
placea bunch of unit tests, since `url.setPath("//foo")` will now result in an invalid (empty) QUrl.
This patch fixes the KIO::mkpath() case.
[1]: http://code.qt.io/cgit/qt/qtbase.git/commit/?id=f62768d046528636789f901ac79e2cfa1843a7b7