dudel.wsgi: correctly find real path of the rest of the code

[dario23]

previously, the abspath() of server.wsgi was added to the python import path. abspath() however only cleans up the given path string, with no filesystem interaction like resolving symlinks etc.

some webservers (like apache2) require .wsgi files to be in an accessible location (like webroot), where for security you might not want to put your whole code, thus encouraging the use of symlinks.