[BUG] Flint job hangs if no streaming job launched

[dai-chen]

What is the bug?

For recover statement, it won't start streaming job at background if the Flint index doesn't exist. Flint job hangs there in this case.

What is the expected behavior?

Flint job stops if no streaming job launched by the SQL statement submitted.

Possible solution is to check if there is streaming job before calling awaitTermination(): https://github.com/opensearch-project/opensearch-spark/blob/main/spark-sql-application/src/main/scala/org/apache/spark/sql/JobOperator.scala#L88

Do you have any additional context?

CREATE INDEX IF NOT EXIST ... WITH (auto_refresh = true) may have same problem.