Fix tests failures by resetting Environment cache

[surgupta-msft]

Issue describing the changes in this PR

resolves #issue_for_this_pr

Pull request checklist

IMPORTANT: Currently, changes must be backported to the in-proc branch to be included in Core Tools and non-Flex deployments.

• Backporting to the in-proc branch is not required
  • Otherwise: Link to backporting PR
• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• My changes do not require diagnostic events changes
  • Otherwise: I have added/updated all related diagnostic events and their documentation (Documentation issue linked to PR)
• I have added all required tests (Unit tests, E2E tests)

Additional information

Additional PR information

[Copilot]

Pull Request Overview

This PR fixes test failures by clearing the environment cache before test execution. The changes ensure that tests using environment variables start with a clean state, preventing interference from previously cached values that could cause intermittent test failures.

Key Changes:

• Added EnvironmentExtensions.ClearCache() calls at the beginning of two test methods that depend on environment variable settings

[jviau]

Consider implementing IDisposable on this test class to run EnvironmentExtensions.ClearCache(); after every test

[surgupta-msft]

/azp run

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