[SPARK-28142][SS] Use CaseInsensitiveStringMap for KafkaContinuousStream

[HeartSaVioR]

What changes were proposed in this pull request?

This patch addresses a missing spot which Map should be passed as CaseInsensitiveStringMap - KafkaContinuousStream seems to be only the missed one.

Before this fix, it has a relevant bug where pollTimeoutMs is always set to default value, as the value of KafkaSourceProvider.CONSUMER_POLL_TIMEOUT is kafkaConsumer.pollTimeoutMs which key-lowercased map has been provided as sourceOptions.

How was this patch tested?

N/A.

[HeartSaVioR]

I skipped adding UT as similar changes for other data source are not covered by UT as well.

[HeartSaVioR]

cc. @cloud-fan

[SparkQA]

Test build #106811 has finished for PR 24942 at commit 8ca7d79.

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

[HyukjinKwon]

Actually, @HeartSaVioR, can we file a JIRA since it fixes an actual bug?

[HeartSaVioR]

Sure, just filed SPARK-28142 and changed the title. Thanks!

[gaborgsomogyi]

LGTM. This lower/natural case is a constant problem.

[gaborgsomogyi]

As I'm implementing DSv2 batch source/sink I've pinpointed similar problems, so creating a PR...

[HyukjinKwon]

Merged to master.

[dongjinleekr]

@gaborgsomogyi @HyukjinKwon Could you have a look for #22282? It is related to this PR.

[HeartSaVioR]

Thanks for reviewing and merging!

[gaborgsomogyi]

@dongjinleekr I've some major items on my plate but coming back to the mentioned PR.

[gatorsmile]

@HeartSaVioR @gaborfeher @HyukjinKwon We should not skip adding the unit test cases. Please add one. Thanks!

[HeartSaVioR]

@gatorsmile Thanks for the suggestion. I'll see whether I can do it with small changes, and raise follow-up PR.

[HeartSaVioR]

#24999 addressed UT. Please review the new patch. Thanks!