added missing cd command in setup_docker_server.rb
added missing cd command in setup_docker_server.rb

byran/cyber-dojo-web,cyber-dojo/web,byran/cyber-dojo-web,byran/cyber-dojo-web,byran/cyber-dojo-web,cyber-dojo/web,cyber-dojo/web,byran/cyber-dojo-web,byran/cyber-dojo-web,byran/cyber-dojo-web,byran/cyber-dojo-web,cyber-dojo/web,byran/cyber-dojo-web