Theatre Royal BathKelly is the raging old stager and Clary his pomposity-puncturing assistant in Ronald Harwood's perennial favourite Any play that contains a show-must-go-on message is bound to resonate in the current climate. That is especially true for the latest production of The Dresser, which is opening a year later than intended. Ronald Harwood's perennial favourite, inspired by his years spent as dresser to S…