Summary:
fix memory leak in db_stress checkpoint test. If s is not ok, checkpoint is not deleted, may cause memory leak.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7813
Test Plan: make asan_check
Reviewed By: cheng-chang
Differential Revision: D25702999
Pulled By: zhichao-cao
fbshipit-source-id: 08253b0852835acb8cfd412503cdabf720afb678