WASHINGTON, March 21 (Reuters) - Billionaire entrepreneur Elon Musk, the world’s richest person, said on Saturday he would cover the paychecks of U.S. Transportation Security Administration officers during their second unpaid work stoppage in six months amid a protracted federal funding lapse. The budget impasse over funding for the TSA’s parent agency, the Department of Homeland Security, is in its fifth week. Screeners and other TSA personnel are days away from missing a second full paycheck, but are being pressured to show up as screening times at some airports stretch on for hours.“I would like to offer to pay the...