Out on Concourse C at Hartsfield-Jackson International Airport, 15 soft, yellow, leather recliners wait to pamper passengers as they await their next flight out of the ATL. In a retail space bright with light from windows overlooking the tarmac, XpresSpa hopes the indignities and distractions that have become commercial flight can melt away at Hartsfield’s first full-service spa.The new salon — set to be one of five at the world’s busiest airport — is part of Hartsfield’s latest retail makeover.