Fixed an issue in S3 Transfer Manager where a thread could get stuck …

[zoewangg]

…waiting for all requests to finish in a downloadDirectory operation

Motivation and Context

#3850

Modifications

Removed the logic to flush buffer when onComplete is invoked. It's not needed because when a request is finished, it should trigger buffer flush automatically. The existing logic could cause the thread that invoked onComplete to starve when there are still requests in flight.

Testing

Ran existing tests

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• I have read the CONTRIBUTING document
• Local run of mvn install succeeds
• My code follows the code style of this project
• My change requires a change to the Javadoc documentation
• I have updated the Javadoc documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed
• I have added a changelog entry. Adding a new entry must be accomplished by running the scripts/new-change script and following the instructions. Commit the new file created by the script in .changes/next-release with your changes.
• My change is to implement 1.11 parity feature and I have updated LaunchChangelog

License

• I confirm that this pull request can be released under the Apache 2 license

[cenedhryn]

Discussed offline, flushing is covered by on next handling and should be safe to remove from onComplete

[zoewangg]

Closing the PR because this did not fully fix the original issue.