The U.S. Justice Department has reportedly opened an antitrust investigation into Ticketmaster’s parent company — a probe that predates the recent Taylor Swift ticket sales debacle. The Justice Department’s antitrust division has been looking into the ticket sales platform’s practices and whether its owner Live Nation Entertainment has a monopoly over the industry, according to a New York Times report Friday citing sources familiar with the matter. The news came after a chaotic presale ticket phase for Swift’s upcoming concert tour, “The Eras Tour,” led to massive technical difficulties, the o…