An amber rainstorm warning and a leaky roof failed to dampen the mood of fans as the Hong Kong Sevens rugby tournament kicked off its 50th anniversary edition on Friday.First-time visitors to the city’s signature annual sporting event expressed amazement at the 50,000-seat Kai Tak Stadium, while a food shortage fiasco that plagued last year’s tournament appeared to have been addressed.Costumed revellers gearing up for three days of rugby could already be seen entering the South Stand –...