Fix invalid setting calls in config/unicorn.rb
Fix invalid setting calls in config/unicorn.rb

* .present? is an AS extension that isn't loaded at this point
* single_process_mode is defined in environment, not at the toplevel

diaspora/diaspora,diaspora/diaspora,Muhannes/diaspora,despora/diaspora,diaspora/diaspora,spixi/diaspora,KentShikama/diaspora,jhass/diaspora,geraspora/diaspora,jhass/diaspora,SuperTux88/diaspora,Muhannes/diaspora,geraspora/diaspora,geraspora/diaspora,despora/diaspora,jhass/diaspora,SuperTux88/diaspora,geraspora/diaspora,spixi/diaspora,KentShikama/diaspora,diaspora/diaspora,jhass/diaspora,Muhannes/diaspora,Flaburgan/diaspora,spixi/diaspora,KentShikama/diaspora,SuperTux88/diaspora,Flaburgan/diaspora,Amadren/diaspora,Amadren/diaspora,Flaburgan/diaspora,Muhannes/diaspora,despora/diaspora,Amadren/diaspora,KentShikama/diaspora,spixi/diaspora,despora/diaspora,Flaburgan/diaspora,Amadren/diaspora,SuperTux88/diaspora