Winding up one of the shortest U.S. Senate careers in history, California's defeated Democratic Senator Pierre Salinger last week announced his resignation, effective Dec. 31. He will take a job as vice president of Beverly Hills' National General Corp., a highly diversified company that operates movie houses in 16 states, deals in real estate and concert talent, and packages candied fruit. Quipped Salinger, 39: "I may be the youngest living ex-Senator in history." Salinger also disclosed that California's Democratic Governor Pat Brown had promised to appoint Republican Senator-elect George Murphy, who beat Pierre in the Nov. 3 election, to fill Salinger's vacancy. That would give Murphy a lead in seniority over his first-term Senate colleagues.