Summary: PR https://github.com/facebook/rocksdb/issues/9557 introduced a race condition between manual compaction foreground thread and background compaction thread. This PR adds the ability to really unschedule manual compaction from thread-pool queue by differentiate tag name for manual compaction and other tasks. Also fix an issue that db `close()` didn't cancel the manual compaction thread. Pull Request resolved: https://github.com/facebook/rocksdb/pull/9625 Test Plan: unittest not hang Reviewed By: ajkr Differential Revision: D34410811 Pulled By: jay-zhuang fbshipit-source-id: cb14065eabb8cf1345fa042b5652d4f788c0c40c