Update fonb-setup.py

i have updated the parser. At first its just removing the existing content with sed command and then echo-ing the simple lines, as discussed. 
As mentioned earlier as well, i couldn't replicate the exact bug, in normal conditions, thus it only malfunctions under abnormalities. The scenario, i imagined was when the key/value settings varies, the config parser was adding an '=' at the end. Since the parser is not working now, all it does is adds the sample lines in place.
echo is not defined in python, so you have to use os.system()