Use Kafka properties when creating AdminClient

[smarsching]

This PR changes AlarmServerMain.ensureKafkaTopics to actually make use of the kafka_props_file parameter, so that custom Kafka properties are used when creating the AdminClient.

Fixes #3625.

@shroffk As you wrote the original code that introduced this problem, you might be the right one to review this PR.

Checklist

• Testing:
  • The feature has automated tests
  • Tests were run
  • If not, explain how you tested your changes

I started the alarm server with the changes and found that the AdminClient now correctly uses the settings set in the Kafka properties file. I checked this by increasing the log level for org.apache.kafka to INFO, so that configuration settings are logged.

• Documentation:
  • The feature is documented
  • The documentation is up to date
  • Release notes:
    • Added an entry if the change is breaking or significant
    • Added an entry when adding a new feature