Summary:
Add an option to db_stress, verify_checksum_one_in, to call DB::VerifyChecksum() once every N ops.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6203
Differential Revision: D19145753
Pulled By: anand1976
fbshipit-source-id: d09edf21f309ad53aa40dd25b7a563d50665fd8b