WORCESTER — Senior golfer Ethan Whitney took medalist honors Monday at the Catholic Conference Showcase by shooting 1-under 69 at Worcester Country Club to lift St. John’s to a second-place finish.The Pioneers (301) were just two strokes behind champion Xaverian. St. John’s Prep (310) was third, followed by BC High (321), Catholic Memorial (360) and Malden Catholic.St. John’s senior teammates Ray Dennehy and Jacob Mrva each carded 76.