Use separate context for Redis mutex unlock

[vlasebian]

Summary

Change the deferred UnlockMutex call to use context.WithoutCancel(ctx) instead of the main ctx. This ensures the unlock Redis command succeeds even if the parent context has been cancelled and the lock gets released faster than the expiration time.

Changes

• Derive a separate context for unlocking the Redis mutex for LockedWatch.

Testing

Steps

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Results

Regressions

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Notes for Reviewers

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Checklist

• Scope: The referenced issue is addressed, there are no unrelated changes.
• Compatibility: The changes are backwards compatible with existing API, storage, configuration and CLI, according to the compatibility commitments in README.md for the chosen target branch.
• Documentation: Relevant documentation is added or updated.
• Testing: The steps/process to test this feature are clearly explained including testing for regressions.
• Infrastructure: If infrastructural changes (e.g., new RPC, configuration) are needed, a separate issue is created in the infrastructural repositories.
• Changelog: Significant features, behavior changes, deprecations and fixes are added to CHANGELOG.md.
• Commits: Commit messages follow guidelines in CONTRIBUTING.md, there are no fixup commits left.