fhir-bucket reindex process should exit with non-zero exit code if it didn't finish with success

[lmsurpre]

Is your feature request related to a problem? Please describe.
In #2752 we fixed an issue so that the fhir-bucket process will exit when it fails (previously it would hang under particular conditions).

However, as implemented, it will always exit with a status code of 0 (success).

For use from kubernetes jobs, it would be nice if it exited with a non-zero exit code.

Describe the solution you'd like
If we know we're exiting without completing the reindex, throw an exception to exit the program.

Describe alternatives you've considered
Rely on processing the output to determine if the reindex completed with success or not.

Acceptance Criteria

1. GIVEN [a precondition]
   AND [another precondition]
   WHEN [test step]
   AND [test step]
   THEN [verification step]
   AND [verification step]

Additional context
Add any other context or screenshots about the feature request here.