Fix NotifyOnFlushCompleted() for atomic flush (#8585)

Summary:
PR https://github.com/facebook/rocksdb/issues/5908 added `flush_jobs_info_` to `FlushJob` to make sure
`OnFlushCompleted()` is called after committing flush results to
MANIFEST. However, `flush_jobs_info_` is not updated in atomic
flush, causing `NotifyOnFlushCompleted()` to skip `OnFlushCompleted()`.

This PR fixes this, in a similar way to https://github.com/facebook/rocksdb/issues/5908 that handles regular flush.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8585

Test Plan: make check

Reviewed By: jay-zhuang

Differential Revision: D29913720

Pulled By: riversand963

fbshipit-source-id: 4ff023c98372fa2c93188d4a5c8a4e9ffa0f4dda

Mention PR 8605 in HISTORY.md (#8619)

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/8619

Reviewed By: riversand963

Differential Revision: D30081937

Pulled By: ltamasi

fbshipit-source-id: 57505957ae2c22d4b194aa28cb3fd261b3b39919