[hotfix] Short circuit judgment for create blob storage dir

[beliefer]

What is the purpose of the change

This PR aims to short circuit judgment for create blob storage dir
According to

flink/flink-runtime/src/main/java/org/apache/flink/runtime/entrypoint/WorkingDirectory.java

Line 49 in df05858

createDirectory(blobStorage);

, there are already existing the blob storage dir.
The original judgment executes baseDir.mkdirs() first, but it returns false. And then we need to execute baseDir.exists().
We can only need execute baseDir.exists() first and short circuit judgment for baseDir.mkdirs().
According to the current code path, I think this is the mainly logic.
And this PR will not lead to any regression even if there exists some corner case.

Brief change log

Short circuit judgment for create blob storage dir

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:

• 1d19be6 Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run azure re-run the last Azure build

[beliefer]

ping @warneke @tillrohrmann cc @1996fanrui @davidradl

[beliefer]

cc @GOODBOY008

[davidradl]

the first thing that mkdirs() does is call exists(). Can we remove the baseDir.exists()?

[beliefer]

Thanks for your reminder. But it let me take a second thinking.
After the second thinking, it's no need to change this line.