fix(instr-redis): don't fail commands when connection pool lacks connection_kwargs

[JamieDanielson]

Description

Redis cluster clients can expose a connection_pool object that doesn't have connection_kwargs. Current instrumentation only checked for existence of connection_pool and would raise an AttributeError if connection_kwargs didn't exist. This change checks for the existence of connection_kwargs and skips adding those attributes if they are not available.

• Related Issue: Redis instrumentation doesn't work properly with Redis Cluster #2505
• Related PR (closed): Fix missing attributes in RedisCluster spans #2626

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• Sync and async tests asserting command completes, span status is UNSET, and no exception is recorded

Does This PR Require a Core Repo Change?

• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• [n/a] Documentation has been updated