NEW ORLEANS — Chaka Khan is more than angry. Instead of getting to rest before her show at the Louisiana Superdome, the R&B star has been booked for two speaking engagements. She’s holed up in her hotel suite, fuming. Outside, her assistants are waiting for her to open the door. Her makeup artist, Derrick Rutledge, is waiting, too. He just flew in to do her after working on Michelle Obama in the East Wing. After New Orleans, he’s scheduled to fly out to do Oprah Winfrey before returning home to Washington. But first Rutledge has to persuade Khan to open...