Handle "NotSupported" status by default implementation of Close() in … (#10127)

Handle "NotSupported" status by default implementation of Close() in … (#10127)

Summary:
The default implementation of Close() function in Directory/FSDirectory classes returns `NotSupported` status. However, we don't want operations that worked in older versions to begin failing after upgrading when run on FileSystems that have not implemented Directory::Close() yet. So we require the upper level that calls Close() function should properly handle "NotSupported" status instead of treating it as an error status.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10127

Reviewed By: ajkr

Differential Revision: D36971112

Pulled By: littlepig2013

fbshipit-source-id: 100f0e6ad1191e1acc1ba6458c566a11724cf466