Summary:
compaction_pri = kMinOverlappingRatio usually provides much better write amplification than the default.
https://github.com/facebook/rocksdb/pull/4907 fixes one shortcome of this option. Make it default.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4911

Differential Revision: D13789262

Pulled By: siying

fbshipit-source-id: d90acf8c4dede44f00d183ca4c7a210259378269