[FLINK-8699][hotfix] Fix in concurrency problem for full Checkpoint.

[sihuazhou]

This PR fix FLINK-8699. In fully checkpoint, kvStateInformation is not a copied object and it can be changed when writeKVStateMetaData() is invoking ... This can lead to problematic, which is serious.

Brief change log

• Copy kvStateInformation to avoid concurrency problem.

Verifying this change

• This change can be verified by the existed unit 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: (yes)
• The S3 file system connector: (no)

Documentation

• Does this pull request introduce a new feature? (no)

[sihuazhou]

@StefanRRichter Could you please have a look?

[StefanRRichter]