Kafka connector can report failure for acknowledgements which eventually succeed

[Azquelt]

Describe the bug

When Message.ack() is called, the kafka connector returns a result as a CompletionStage which completes when the kafka commit operation has completed successfully.

In some cases, the kafka commit operation can fail and report a retriable exception. Currently, the Kafka connector fails the CompletionStage with this retriable exception, but then goes on to run a commit operation for a later offset, causing the earlier messages to be succesfully commit.

Steps to Reproduce
Cause the kafka connector to report a retriable exception

Expected behavior
The ack() result should not complete until the commit operation has been retried and either fails with a fatal exception or succeeds.

Diagnostic information:

• OpenLiberty Version: current master

Additional context
Found through automated testing