add IngestService to context manager

[khangich]

Description

Make RedisIngestService lifecycle management more explicit. It can help with redis warm up connections and gracefully shutdown.

Feature request: https://github.com/NVIDIA/nv-ingest/issues/969

Checklist

• [ ] I am familiar with the Contributing Guidelines.
• [ ] New or existing tests cover these changes.
• [ ] The documentation is up to date with these changes.
• [ ] If adjusting docker-compose.yaml environment variables have you ensured those are mimicked in the Helm values.yaml file.

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[drobison00]

@khangich Thanks for the PR!