Columbia Pictures began cleaning house Tuesday, dismissing at least 30 production and marketing executives in Los Angeles and New York--including many who had been hired by or associated with former Columbia chairman David Puttnam. Industry observers and Columbia executives had expected layoffs at the Coca-Cola film unit as a prelude to its merger with Tri-Star Pictures under the Columbia Pictures Entertainment banner. Most prominent among the pink-slipped was worldwide production president Fred Bernstein, but many vice-presidents and directors also were fired. Columbia sources said Wednesday that the company's sales-distribution and international divisions were also being pruned. Tri-Star chairman Victor Kaufman--who will head up the new Columbia Pictures Entertainment company--was not available for comment Wednesday.