fixed check funtion in mgmtroot directory

[iyartsev]

os.path.join(id, name) leads to incorrect paths if running under Windows. Diectory paths in management root use always "/" no matter where the script is run.

[iyartsev]

I added another commit that fixes mappingrule.set:
If there was a mapping rule "Map" with js file "map.js" and the mapping rule is uploaded with a new name "NewMap" but the same java script file name (it happens, wenn the name is changed) it caused an exception. Now it is checked if the mapping rule with the same javascipt file nae already exists and if so, this mapping rule is deleted before adding the new one.