IT’S a measure of the star power emanated by Bruce Springsteen that a person as uniquely magnetic as “Little” Steven Van Zandt should achieve fame largely through being his sideman. The famously expressive guitarist with Springsteen’s E-Street Band throughout their career together, Van Zandt appeared here with his own backing group the Disciples of Soul – an expansive ensemble featuring a five-piece horn section and a trio of energetic backing singers and dancers – and took on the role of frontperson all by himself.