[SPARK-11194] [SQL] [BRANCH-1.5] [WIP] Use MutableURLClassLoader for the classLoader in IsolatedClientLoader.

[yhuai]

This PR is a test fix for SPARK-11194 in branch 1.5. However, since it fundamentally changes the way that we do add jar in branch 1.5, we will not merge it into 1.5 branch.

[SparkQA]

Test build #43942 has finished for PR 9171 at commit c06d9ac.

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

[yhuai]

test this please

[SparkQA]

Test build #43959 has finished for PR 9171 at commit c06d9ac.

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

[yhuai]

I think that this pr also suffers the same problem exposed in #9170. There was no test failure because we only set the mutable classloader when we actually do add jar (In #9170 we set the mutable classloader to executionHive.state.getConf whenever we need to use withHiveState).

[yhuai]

I have changed the classloader to a non-closable mutable url class loader.

[SparkQA]

Test build #44233 has finished for PR 9171 at commit 7951df1.

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

[davies]

LGTM

[yhuai]

Cool thanks for reviewing it. I will close it since it will not go in 1.5 branch.