By KAROUN DEMIRJIAN and MADELEINE NGO Many Department of Homeland Security employees were on track to miss a paycheck last Friday amid the nearly monthlong lapse in funding for the agency, leading officials to warn of potential disruptions in air travel if more airport security workers call out of work. Travelers have already experienced long security line delays at some major airports, including John F. Kennedy International Airport in New York and William P. Hobby Airport in Houston, as...