By Nandita Bose and Jeff Mason WASHINGTON (Reuters) -Former President Barack Obama returned to the White House on Tuesday for the first time since leaving office in 2017 to tout the benefits of his signature healthcare law and bolster his friend and former governing partner, President Joe Biden. Obama arrived in the East Room to robust cheers from the assembled crowd of Congress members and administration staffers, and remarked on the changes that had been made in the White House since he was last there – notably the arrival of a feline. “There’s a cat running around,” he said to laughter, “wh…