For nearly two decades Dave Portnoy made his life and his company, Barstool Sports, into an online reality show of sorts — oversharing everything from office friction to his own dating life. Now he’s written a memoir. With so much already out there, why go through the trouble? “Ego,” Portnoy humbly told me. “The thought of walking into an airport and seeing this book in all the bookshops really appealed to me.” The Barstool honcho was tempted by the possibility that his book, “ Cancel Me If You