By Greg Bishop Tyrann Mathieu’s journey to his hometown team has been long and difficult. A feel-good story? It’s not that simple. Classes at Northshore High School are in session, but no one bothers the NFL veteran strolling from the parking lot toward the football field. That’s part of the balance he’s seeking, what’s necessary for the task ahead. He could drive to his hometown of New Orleans in under 40 minutes, and yet, he’s here, in Slidell, La., and not there, intentionally, just far enough away. It’s a random July weekday, as Tyrann Mathieu carries a bright yellow backpack adorned with …