NEW YORK, March 20 (Reuters) - Workers erected barricades around a Manhattan courthouse on Monday as New York City braced for a possible indictment of Donald Trump over an alleged hush-money payment to porn star Stormy Daniels during his 2016 campaign. Trump has denied that any such affairs took placeThe Manhattan District Attorney's office had asked that Cohen be available as a rebuttal witness, but he was told on Monday afternoon that his testimony was not needed, according to his lawyer Lanny Davis. Trump is also seeking to delay a civil fraud trial, scheduled for Oct