2da53b1e06
Summary: 1. Check status of CreateNewBackup. If status is not OK, then throw. 2. Add purgeOldBackups API Test Plan: make test make sample Reviewers: haobo, sdong, zzbennett, swapnilghike, yhchiang Reviewed By: yhchiang Subscribers: leveldb Differential Revision: https://reviews.facebook.net/D21753