OAKLAND, Calif. — A two-game sweep of the A’s was just what the Giants needed to regain a little grip on their postseason hopes. Their playoff viability was thrown further into question after suffering a four-game sweep series to the juggernaut Dodgers at Oracle Park earlier this week, extending their losing streak against Los Angeles to eight for the first time since 1979. They’re still technically in reach of a wild card spot, and a little momentum created with a 6-4 win on Sunday afternoon in front of a crowd of around 31,000 in Oakland doesn’t hurt. Starter Logan Webb was strong in his out…