Summary:
Delete column family handlers before deleting db to avoid `last_ref`
assert.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8564
Test Plan: Inject compaction test in db_stress test
Reviewed By: pdillinger
Differential Revision: D29797375
Pulled By: jay-zhuang
fbshipit-source-id: e8baf4d279f4db5d963db95c9445454156205501