FLOWERY BRANCH — Robert McClain was one of those offseason signings that hardly anyone notices. A seventh-round draft pick, he had already been cut by two teams when he caught on with the Atlanta Falcons.The 5-foot-9 cornerback turned out to be a steal. McClain has been a huge part of the Falcons’ injury plagued secondary, which lost star cornerback Brent Grimes in the very first game and is now dealing with Asante Samuel’s ailing right shoulder.