TORONTO — The past couple of seasons have been a struggle for the Pistons. That is, unless they’re playing the Toronto Raptors. Since he arrived in Detroit, coach Dwane Casey is 8-3 against his former team, including two wins this season. Make it 9-3. The Pistons completed the series sweep this season, with a 108-106 victory on Thursday night at Scotiabank Arena. Through the first 34 minutes, the Pistons played one of their best games of the season, but they had to hold on through a drought without a field goal for a stretch bridging the third and fourth quarters. They got back on track and he…