When a major band’s album leaks online, it’s customary to either steadfastly ignore the event or throw an ineffectual, Jack White-style tantrum. But when Incubus’s new record (fittingly titled If Not Now, When?) turned up online several months in advance, the biggest surprise wasn’t that people were this eager to see what the 20-year-old rock outfit were up to; it was the band’s response… …