“Phone rings, door chimes, in comes… Company?” That refrain is one of Stephen Sondheim’s greatest earworms (second only perhaps to “Bobby, Bobby baby, Bobby bubi, Robby,” etc. in the same song). And, in the shaky touring production of Marianne Elliott’s inventive reimagining of the beloved musical, playing at the Kennedy Center through March 31, it presents more like a cautious question than a confident declaration.