LINCOLN — Asked what would make this season a success, Nebraska running back Rahmir Johnson didn’t need time to think about it.He’s had an offseason to do that, and the goals are straightforward anyway.Johnson wants the Huskers to earn bowl eligibility for the first time since he arrived in Lincoln. He wants to contend for a Big Ten championship, punch a ticket to the expanded College Football Playoff and — if the cards fall right, he said — play for a national title.But one thing, in particular, topped the list.“Staying healthy,” he said Tuesday during NU media day. “That would be successful.” A sixth-year senior, Johnson showed flashes at the beginning of last season before suffering a shoulder dislocation, one that required season-ending surgery, in the Huskers’ Week 3 win over Northern Illinois. People are also reading… It wasn’t the first time, either.The same thing happened to Johnson in 2021, his first year as an integral part of NU’s backfield. He was the team’s second-leading…