Summary:
When called on transactions, MultiGet could return a legit MergeInProgress status. The patch excludes this case from errors.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6257
Differential Revision: D19275787
Pulled By: maysamyabandeh
fbshipit-source-id: f7158229422af015947e592ae066b4273c9fb9a4