Agence France-Presse: British energy giant BP says it has temporarily stopped oil flowing into the Gulf of Mexico for the first time in three months as it began key tests hoping to stem the spill for good. Shortly after BP engineers shut down the last of three valves on a giant new cap placed on the blown-out well at around 2:25 pm (1925 GMT) Thursday, senior vice president Kent Wells announced no oil was leaking into the sea. “I’m very excited to see no oil flowing into the Gulf of Mexico,” Wells …