[v2] contrib/IBM/sarama.v1: skip integration test if env variable is not set

[rarguelloF]

What does this PR do?

Port of #3092

Motivation

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.
• For internal contributors, a matching PR should be created to the v2-dev branch and reviewed by @DataDog/apm-go.

Unsure? Have a question? Request a review!

[datadog-datadog-prod-us1]

Datadog Report

Branch report: rarguelloF/v2-ibm-sarama-skip-integration-test
Commit report: 563ffe2
Test service: dd-trace-go

✅ 0 Failed, 4084 Passed, 64 Skipped, 2m 40.46s Total Time

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-01-16 15:00:06

Comparing candidate commit 38162f3 in PR branch rarguelloF/v2-ibm-sarama-skip-integration-test with baseline commit 5f5d66d in branch v2-dev.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 51 metrics, 2 unstable metrics.