By Mark Lamport-Stokes OAKMONT, Pennsylvania (Reuters) - The 116th U.S. Open has not yet reached its halfway point after thunderstorms wreaked havoc in the opening round but Dustin Johnson has already emerged as the player to beat. The American power hitter, seeking redemption for his agonizing near-miss at Chambers Bay last year, has played the best golf of the week from tee to green to hold the clubhouse lead after 36 holes. "He played awesome," said Spaniard Sergio Garcia, who has played in Johnson's company at Oakmont. More...