Summary:
allow_concurrent_memtable_write is incompatible with non-zero max_successive_merges. Although we check this at runtime, we currently don't prevent the user from setting this combination in options. This has led to stress tests to fail with this combination is tried in ::SetOptions. The patch fixes that.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6254

Differential Revision: D19265819

Pulled By: maysamyabandeh

fbshipit-source-id: 47f2e2dc26fe0972c7152f4da15dadb9703f1179