Jay-Z has got the nerves bad.In fact, the 45-year-old pop superstar — who was recruited by Jay-Z and his Roc Nation company to headline the Super Bowl LVIII halftime show on Sunday — defended the 54-year-old rapper for his tense takedown of the Grammys on music’s biggest night last Sunday.“I think I like a nervous Jay-Z more than anything. That’s what it told me,” Usher told The Post about the hip-hop mogul’s speech when he was accepting the Dr.