Summary:
If IsInSnapshot(seq2, snapshot) determines that the snapshot is released, the future queries IsInSnapshot(seq1, snapshot) could still return a definitive answer of true if for example seq1 is too old that is determined visible in all snapshots. This violates a recently added assert statement to compaction iterator. The patch relaxes the assert.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4969

Differential Revision: D14030998

Pulled By: maysamyabandeh

fbshipit-source-id: 6db53db0e37d0a20e8997ef2c1004b8627614ab9