By Maria Golovnina and Guy Faulconbridge LONDON (Reuters) - A British soldier was hacked to death by two men shouting Islamic slogans in a south London street on Wednesday, in what the government said appeared to be a terrorist attack. A dramatic clip filmed by an onlooker just minutes after the killing showed a man with hands covered in blood, brandishing a bloodied meat cleaver and a knife. "We swear by almighty Allah we will never stop fighting you. ...