[SPARK-26491][K8S][FOLLOWUP] Fix compile failure

[dongjoon-hyun]

What changes were proposed in this pull request?

This fixes the compilation error.

$ cd resource-managers/kubernetes/integration-tests
$ mvn test-compile
[ERROR] /Users/dongjoon/APACHE/spark/resource-managers/kubernetes/integration-tests/src/test/scala/org/apache/spark/deploy/k8s/integrationtest/KubernetesTestComponents.scala:71: type mismatch;
 found   : org.apache.spark.internal.config.OptionalConfigEntry[Boolean]
 required: String
[ERROR]       .set(IS_TESTING, false)
[ERROR]            ^

How was this patch tested?

Pass the Jenkins K8S Integration test or Manual.

[SparkQA]

Test build #101007 has finished for PR 23505 at commit 677ab2c.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Kubernetes integration test starting
URL: https://amplab.cs.berkeley.edu/jenkins/job/testing-k8s-prb-make-spark-distribution-unified/6884/

[SparkQA]

Kubernetes integration test status success
URL: https://amplab.cs.berkeley.edu/jenkins/job/testing-k8s-prb-make-spark-distribution-unified/6884/

[dongjoon-hyun]

K8S integration test passed.

cc @vanzin and @mgaido91 .

[dongjoon-hyun]

Thank you for review and approval, @felixcheung .
Merged to master.

[mgaido91]

a late LGTM, thanks for teh fix @dongjoon-hyun !

[dongjoon-hyun]

Thanks, @mgaido91 .

[ifilonenko]

I don't see this PR merged into master. My integration tests are still failing

[dongjoon-hyun]

@ifilonenko .
Please see b316ebf

[ifilonenko]

That's odd I am looking at master and see:
https://github.com/apache/spark/blob/master/resource-managers/kubernetes/integration-tests/src/test/scala/org/apache/spark/deploy/k8s/integrationtest/KubernetesTestComponents.scala#L71 the previous

[dongjoon-hyun]

Another commit breaks it again. I'll make a follow up for SPARK-26482.