Frédéric Olivieri had been director of the Milan opera house’s ballet company from 2002 to 2007. His successor, Makhar Vaziev, left in late 2015 to bring order to the wildly-troubled Bolshoi Ballet; his successor, modern-dance choreographer Mauro Bigonzetti, was a poor fit with Italy’s most august classical ballet company and resigned after eight months. So the return of a familiar face with a steady hand was greeted by La Scala’s dancers with applause.