[FLINK-9127] [Core] Filesystem State Backend logged incorrectly

[skidder]

What is the purpose of the change

This pull-request fixes a message logged when during startup of the Flink Task-Manager and Job-Manager when a filesystem backend is in use.

The old incorrect behavior produced a log message indicating that a heap-memory backend is use in.

Brief change log

• Fix the log message produced by the StateBackendLoader class in Core.

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

Documentation

• Does this pull request introduce a new feature? no

[bowenli86]

The original logging is correct - filesystem state backend is actually memory state backend + filesystem checkpointing. No need to change the logging.