fix(redis): define result for try/catch [backport 2.10]

[github-actions]

Backport 3d8ba40 from #9786 to 2.10.

Prior to this change one of the redis_utils functions attempted to call a function in a try/catch with result=result with result being defined within the try.

This caused "undefined variable" errors to be raised when the exception was hit.

After this change, result is initialized as None before the try/catch, preventing the "undefined variable" errors"

Checklist

• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: backport-9786-to-2.10
Commit report: 6e7f8f0
Test service: dd-trace-py

✅ 0 Failed, 352 Passed, 541 Skipped, 8m 5.72s Total duration (3m 21.29s time saved)

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-07-19 13:10:38

Comparing candidate commit 352d456 in PR branch backport-9786-to-2.10 with baseline commit bbbc041 in branch 2.10.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 213 metrics, 9 unstable metrics.