[SPARK-32665][SQL][TEST] Deletes orphan directories under a warehouse dir in SQLQueryTestSuite

[maropu]

What changes were proposed in this pull request?

In case that a last SQLQueryTestSuite test run is killed, it will fail in a next run because of a following reason:

[info] org.apache.spark.sql.SQLQueryTestSuite *** ABORTED *** (17 seconds, 483 milliseconds)
[info]   org.apache.spark.sql.AnalysisException: Can not create the managed table('`testdata`'). The associated location('file:/Users/maropu/Repositories/spark/spark-master/sql/core/spark-warehouse/org.apache.spark.sql.SQLQueryTestSuite/testdata') already exists.;
[info]   at org.apache.spark.sql.catalyst.catalog.SessionCatalog.validateTableLocation(SessionCatalog.scala:355)
[info]   at org.apache.spark.sql.execution.command.CreateDataSourceTableAsSelectCommand.run(createDataSourceTables.scala:170)
[info]   at org.apache.spark.sql.execution.command.DataWritingCommandExec.sideEffectResult$lzycompute(commands.scala:108)

This PR intends to add code to deletes orphan directories under a warehouse dir in SQLQueryTestSuite before creating test tables.

Why are the changes needed?

To improve test convenience

Does this PR introduce any user-facing change?

No

How was this patch tested?

Manually checked

[SparkQA]

Test build #127684 has finished for PR 29488 at commit 4681e62.

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

[dongjoon-hyun]

+1, LGTM. Thanks, @maropu .
Merged to master for Apache Spark 3.1.0 on December 2020.

[maropu]

Thank you for your quick response, @dongjoon-hyun !