KABUL (AP) — The killing of five British troops by a rogue Afghan policeman underlines concerns about training and discipline within the ranks and possible insurgent infiltration of a police force that the U.S. hopes will be its ticket out of Afghanistan someday.The attack caused anguish in Britain, where public support for the war has been waning. Britain is the largest contributor to NATO forces in Afghanistan after the United States, and its continued presence there is central to President Obama’s strategy as he weighs dispatching tens of thousands more U.S. troops.–Contact The Daily Reveille’s news staff at [email protected]