Logs are cluttered with warning messages around the additional seed service

[adejanovski]

When no endpoint exists in the additional seeds service, we constantly see warnings in the logs complaining about not being able to connect to it:

2024-10-04T09:48:58.330Z cass50-dc1-r1-sts-0 WARN Seed provider couldn't lookup host cass50-dc1-additional-seed-service

We could workaround this by adding one of the local seeds endpoint into that service if it's empty. This would allow getting rid of the warnings while keeping the advantage we get out of this service (which is to avoid modifying the spec when the value changes, not requiring a rolling restart of the pre-existing DC).

┆Issue is synchronized with this Jira Story by Unito
┆Issue Number: K8OP-265