Revert "[SPARK-21428] Turn IsolatedClientLoader off while using builtin Hive jars for reusing CliSessionState

[cloud-fan]

This reverts commit b83b502.

It has a regression as reported in #19068 (comment) , seems the fix is not trivial, we should revert this commit first.

This revert has some conflicts, so try to go through jenkins to avoid to mess up something.

[cloud-fan]

cc @yaooqinn @jiangxb1987

[yaooqinn]

ok to me, more tests are needed on #18648

[SparkQA]

Test build #81908 has finished for PR 19273 at commit 72c5a8e.

• This patch fails due to an unknown error code, -9.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #81915 has finished for PR 19273 at commit 72c5a8e.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[cloud-fan]

closing it as the regression is fixed by #19068

[SparkQA]

Test build #81922 has finished for PR 19273 at commit 72c5a8e.

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