Improve logging for lookups

[aho135]

Description

"Coordinator is unavailable" overstates the problem here. This gets logged even when the coordinator is available but no lookups have been configured.

Changed log message from "Coordinator is unavailable" to "Could not fetch lookups from the coordinator"

Release note

Improved logging when ingestion tasks try to get lookups from the coordinator at startup

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Key changed/added classes in this PR

• LookupReferencesManager

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This PR has:

• been self-reviewed.
• added documentation for new or modified features or behaviors.
• a release note entry in the PR description.
• added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
• added or updated version, license, or notice information in licenses.yaml
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• added integration tests.
• been tested in a test Druid cluster.

[kfaraz]

Slight rephrase:

Suggested change

	LOG.info("No lookup list found from coordinator. Loading saved snapshot instead");
	LOG.info("Could not fetch lookups from the coordinator. Loading saved snapshot instead.");

[kfaraz]

Merging as IT failure is unrelated.