STUDY TO EVALUATE IMMUNOGENICITY AND SAFETY OF GSK BIOLOGICALS' HERPES ZOSTER SUBUNIT (HZ/SU) VACCINE AT 9 AND 10 YEARS AFTER VACCINE ADMINISTRATION AND ASSESSMENT OF RE-VACCINATION WITH 2 ADDITIONAL DOSES AT 10 YEARS AFTER INITIAL VACCINATION, IN HEALTHY SUBJECTS AGED 60 YEARS OF AGE(YOA) AND OLDER: