Abu Dhabi, Sept. 19 -- Sri Lanka qualified in style for the Super Four by beating Afghanistan by six wickets in their final Asia Cup group game here on Sunday. In the process, they also knocked Afghanistan, semi-finalists of the T20 World Cup last year, out of the continental event. Chasing a stiff target of 170, Sri Lanka rode on a fine unbeaten knock of 74 from opener Kusal Mendis. Kusal Perera and Kamindu Mendis also made vital contributions as Sri Lanka got home with eight balls to spare. Earlier, Sri Lanka pacer Nuwan Thushara (4/18) struck thrice in his lethal opening spell before Mohammed Nabi struck five sixes in the final over to lead Afghanistan's sensational recovery that fired them to 169/8....