His start canceled by rain, Jake Peavy sat in front of a computer and sang while strumming his guitar. Peavy was practicing for the Woodjock Jam Fest, a charity event this Wednesday in Scottsdale, Ariz. On the field he’s getting ready for what he hopes will be a healthy season. After the Chicago White Sox game Sunday against the Cubs was canceled because of rain, the right-hander threw 45…


