Summary:
previously if `checkpoint_dir` contained a trailing slash, we'd attempt to create the `.tmp` directory under `checkpoint_dir` due to simply concatenating `checkpoint_dir + ".tmp"`. This failed because `checkpoint_dir` hadn't been created yet and our directory creation is non-recursive. This PR fixes the issue by always creating the `.tmp` directory in the same parent as `checkpoint_dir` by stripping trailing slashes before concatenating.
Closes https://github.com/facebook/rocksdb/pull/3275
Differential Revision: D6574952
Pulled By: ajkr
fbshipit-source-id: a6daa6777a901eac2460cd0140c9515f7241aefc
f3fe6f883b