MELBOURNE, Australia — Novak Djokovic choked back tears as he paid tribute to Kobe Bryant, the Los Angeles Lakers great who died in a helicopter crash on Sunday. After moving within two wins of an eighth Australian Open title with a win over Milos Raonic, Djokovic then wore a green jacket with the letters KB and the numbers 8 and 24 embroidered on the chest and a red heart beneath the numbers. In an on-court interview with John McEnroe, the 16-time major winner was visibly upset when he spoke about his friendship with Bryant.