Summary: include db_stress_tool in rocksdb tools lib Test Plan (on devserver): ``` $make db_stress $./db_stress $make all && make check ``` Pull Request resolved: https://github.com/facebook/rocksdb/pull/5950 Differential Revision: D18044399 Pulled By: riversand963 fbshipit-source-id: 895585abbbdfd8b954965921dba4b1400b7af1b1