The Cleveland Cavaliers were swept out of the Eastern Conference Finals at the hands of the New York Knicks. The Cavaliers are bringing back head coach Kenny Atkinson, according to several reports . Atkinson won NBA coach of the year during his first season with the team and got the Cavaliers to the conference finals in his second year.  But there’s one glaring mistake that the Cavs can’t afford to repeat this offseason. The Cavs can’t ignore championship mindsets. Returning Atkinson makes logical sense, as he’s made incremental progress with this team since arriving in Cleveland. But Atkinson’s remarks about “analytical wins” completely missed the mark. So did veteran point guard James Harden’s postgame remarks after Game 4, where the 36-year-old believed the Cavs were better than the Knicks despite getting swept. This shows a locker room that lacks accountability. This offseason, the Cavs must add players that bring a championship identity. Harden is a serial playoff underachiever.…