Perhaps the first thing one notices when listening to the Hot Club of Cowtown is its lack of irony, self-consciousness and forced hipness in embracing a style of music that so easily lends itself to such things. On the trio’s fourth album, ”Ghost Train” (Hightone), the band not only cavorts with string-band jazz and western swing, but it also performs the Aerosmith song ”Chip Away the Stone” in this style — with tongue firmly out of cheek…