[BUGFIX] Fix how we look up the client context

[Czechh]

What does this PR do?

While manually testing my changes for distribuited tracing I found this error - TypeError: argument of type 'ClientContext' is not iterable

This PR modifies how we access the custom attribute in the client_context object.

Motivation

Testing Guidelines

Additional Notes

Types of Changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

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