SEOUL (Reuters) - Boasting an overgrown beard and grey wavy hair, 65-year-old Kim Chil-doo glared into the wall, poised and confidant, as he practiced his runway walk among young, pin-thin models at an academy in Seoul earlier this month. A South Korean senior model Kim Chil-doo, 65-years-old, attends a practice session in Seoul, South Korea,…