Jan 31 (Reuters) – Switzerland took advantage of Novak Djokovic’s absence to open a 2-0 lead over last year’s runners-up Serbia in their Davis Cup tie on Friday with Roger Federer and Stanislas Wawrinka winning their singles rubbers. Two months after their defeat by Czech Republic in the final, Serbia fielded a second-string team who were quickly put under pressure in their World Group first round clash. Federer beat 268th-ranked Ilija Bozoljac 6-4 7-5 6-2 while Wawrinka, fresh from winning his maiden grand slam title at the Australian Open, eased past Dusan Lajovic 6-4 4-6 6-1 7-6(7). …