[SPARK-21783][SQL]Turn on ORC filter push-down by default

[vinodkc]

What changes were proposed in this pull request?

Turned on ORC filter push-down option by default, spark.sql.orc.filterPushdown was turned off by default from the beginning.

How was this patch tested?

Updated existing test cases

[dongjoon-hyun]

Ur, I made the PR two days ago already, #18991

[vinodkc]

Ok , I'm closing my PR.
Now a days, Spark JIRA is not showing PR status.That is why I missed your PR.

[SparkQA]

Test build #80906 has finished for PR 19007 at commit 8756a54.

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

[SparkQA]

Test build #80907 has finished for PR 19007 at commit 2c46907.

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