[HUDI-3450] Avoid passing empty string spark master to hudi cli

[zhedoubushishi]

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What is the purpose of the pull request

When not passing SparkMaster, by default Hudi CLI should use SparkUtil.DEFAULT_SPARK_MASTER. However, w/ a recent code change in OSS, when SparkMaster is not passed, it would set Spark master to "" which causes the following exception when initializing a Hudi CLI job:

{{org.apache.spark.SparkException: Could not parse Master URL: ''at org.apache.spark.SparkContext$.org$apache$spark$SparkContext$$createTaskScheduler(SparkContext.scala:2999)

at org.apache.spark.SparkContext.<init>(SparkContext.scala:567)

at org.apache.spark.api.java.JavaSparkContext.<init>(JavaSparkContext.scala:58)

Brief change log

Verify this pull request

This change added tests and can be verified as follows:

• Added testGetDefaultSparkConf to verify the change.

Committer checklist

• Has a corresponding JIRA in PR title & commit

• Commit message is descriptive of the change

• CI is green

• Necessary doc changes done or have another open PR

• For large changes, please consider breaking it into sub-tasks under an umbrella JIRA.

[XuQianJin-Stars]

!sparkMaster.get().isEmpty() -> !sparkMaster.get().trim().isEmpty()

[zhedoubushishi]

Changed.

[nsivabalan]

@zhedoubushishi : can you address comments when you get a chance.
@XuQianJin-Stars : once you approve it, let me know. I can merge it in.

[zhedoubushishi]

@nsivabalan Resolved the comment.

[hudi-bot]

CI report:

• 63bb52d Azure: SUCCESS

Bot commands

@hudi-bot supports the following commands:

• @hudi-bot run azure re-run the last Azure build

[XuQianJin-Stars]

@zhedoubushishi : can you address comments when you get a chance. @XuQianJin-Stars : once you approve it, let me know. I can merge it in.

I approve it

[XuQianJin-Stars]

LGTM , Thanks @zhedoubushishi