Allison Reid is great at lion. She may have been on Hofstra University’s track and cross country team, but it’s been Reid’s sworn secret that’s really kept the 22-year-old on her toes the past four years. The East Northport runner lived a covert double life as the school’s mascot, Kate the Lioness, and was the first student-athlete to do so in decades — if ever. “My suitemates didn’t know, teammates didn’t know, and my coach didn’t know,” Reid told The Post days after graduation.  “Nobody on