Pianist/conductor Daniel Barenboim says he’s cutting back his schedule. But “the Chicago Symphony Orchestra music director’s idea of cutting back in his 61st year (he turned 60 last November) might still seem exhausting to a mere mortal. He’s just completing his annual Festtage (Festival Days) in Berlin, which included two performances each at his own opera house of Wagner’s “Tristan und Isolde” and Verdi’s “La Traviata,” an opera he had never conducted before, as well as three performances by the CSO at the world-renowned Philharmonie, the home of the Berlin Philharmonic Orchestra, of six heavy-duty works by Mahler and Bruckner.”