how to unroot a rooted android device? 
the following routine worked my android 4.4:
1.uninstall every rooting app on the device.
2.install this version of "super su" app.
3.run it.
4. click on continue button for the first question it asks
5.for the second question click "normal".
6. upgrade the app to latest version and answer the question as befor.
7.on setting section click on "fully unroot..."
8.wait until finish and restart