Bugfix: Removing pointless fastcgi_index parameter

fastcgi_index applies only if url ends with /, so it is useless for `\.php$` anyway. 

For /, we already supply SCRIPT_FILENAME, so it gets messy if we supply both - and breaks the APIs, since fastcgi_index would be appended to all calls ending with /

http://wiki.nginx.org/HttpFastcgiModule#fastcgi_index

fixes easybib/issues#1180