Summary:
Recently, periodic compaction got turned on by default for leveled compaction is compaction filter is used. Since periodic compaction is now supported in universal compaction too, we do the same default for universal now.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5994

Test Plan: Add a new unit test.

Differential Revision: D18363744

fbshipit-source-id: 5093288ce990ee3cab0e44ffd92d8489fbcd6a48