Fix install via UI when "Intranet" is selected

#4084 

Installation is now without errors. Note however that this is done with ```max_execution_time = 300``` in php.ini.

![selection_019](https://f.cloud.github.com/assets/4497748/1418147/f93821e2-3faa-11e3-9b36-1404c929aa8c.png)