Connect: Fix coordinator consumer group on iceberg control topic with…

[rainerschamm]

• Fixes Kafka Connect: Coord consumer group on iceberg control topic with phantom consumer after stopping a connector #17349

[uros-b]

@rainerschamm This seems to be overlapping with #16843. cc @hkwi

[rainerschamm]

@rainerschamm This seems to be overlapping with #16843. cc @hkwi

Ah yes thanks, there is a bit of overlap.

[hkwi]

Thank you for reporting this in #17349 and for following up with the fix in
#17350. It looks like we independently ran into the same coordinator shutdown
issue.

I reviewed both #17349 and #17350, and I believe #16843 already covers the
reported failure mode. #16843 makes CoordinatorThread.terminate() wait for
the coordinator thread to exit, so the shutdown path reaches
coordinator.stop() before task shutdown continues. It also checks whether
the thread is still alive after the timeout and propagates interruption or
termination failures.