[FLINK-28800][network] HsFileDataManager should avoid busy-loop when fileReader has not data to read

[reswqa]

What is the purpose of the change

When fileReader has no data to read, for example, most of the data is consumed from memory. HsFileDataManager will encounter busy-loop problem, which will lead to a meaningless surge in CPU utilization and seriously affect performance.

Brief change log

• Sleep a very short time for HsFileDataManager once read empty.

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no

[flinkbot]

CI report:

• 9fffec9b0efcca555b47a82c13c8a746816d233a Azure: SUCCESS

Bot commands

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[reswqa]

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