By Guy Faulconbridge and Michael Holden LONDON (Reuters) - Two British men of Nigerian descent accused of hacking a soldier to death on a London street in revenge for wars in Muslim countries were known to security services, a source close to the investigation said Thursday. One man, filmed calmly justifying the killing as he stood by the body holding a knife and meat cleaver in bloodied hands, was named by acquaintances as 28-year-old Londoner Michael Adebolajo - a British-born convert to radical Islam. ...