[FLINK-13739][table-blink] JDK String to bytes should specify UTF-8 encoding

[JingsongLi]

What is the purpose of the change

The reason should be that the default encoding of the machine is not UTF-8, and the test relies on the default encoding.
The code should use the specified UTF-8 encoding

Verifying this change

This change is already covered by existing tests

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, Yarn/Mesos, ZooKeeper: no
• The S3 file system connector:no

Documentation

• Does this pull request introduce a new feature? no

[flinkbot]

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Automated Checks

Last check on commit e628a7a (Fri Aug 23 10:20:00 UTC 2019)

Warnings:

• No documentation files were touched! Remember to keep the Flink docs up to date!

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Review Progress

• ❓ 1. The [description] looks good.
• ❓ 2. There is [consensus] that the contribution should go into to Flink.
• ❓ 3. Needs [attention] from.
• ❓ 4. The change fits into the overall [architecture].
• ❓ 5. Overall code [quality] is good.

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CI report:

• e28534c : CANCELED Build
• e628a7a : SUCCESS Build

[rmetzger]

I'm testing the change

[rmetzger]

[INFO] Results:
[INFO]
[INFO] Tests run: 668, Failures: 0, Errors: 0, Skipped: 0

Looks like this PR is fixing the issue.

[JingsongLi]

Thanks @rmetzger for verification, ping @wuchong to review

[wuchong]

Thanks for the fixing @JingsongLi . It looks good to me.

I will merge it.