Correct checking instance type of get data response

[vivek-datadog]

What does this PR do?

_get_data generic exception handler was incorrectly checking for resp variable which would always result in False when the status code is not in successful range

I believe the intent was to ensure the presence of resp variable to avoid an exception inside the generic exception handler

As a result, a critical service check was sent whenever http request in _get_data fails leading to support ticket AGENT-10055

This change ensures that the correct existence of resp variable and the relevant status code, so that auth error is raised as per expectations

Motivation

AGENT-10055

Additional Notes

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Changelog entries must be created for modifications to shipped code
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.

[github-actions]

Test Results

     24 files       24 suites   6m 58s ⏱️
   121 tests    118 ✔️   3 💤 0 ❌
1 464 runs  1 374 ✔️ 90 💤 0 ❌

Results for commit cf6bfa2.

♻️ This comment has been updated with latest results.

[codecov]

Codecov Report

Merging #15554 (f87b658) into master (8dd02f3) will increase coverage by 0.34%.
The diff coverage is 100.00%.

❗ Current head f87b658 differs from pull request most recent head cf6bfa2. Consider uploading reports for the commit cf6bfa2 to get more accurate results

Flag	Coverage Δ
elastic	93.75% <100.00%> (+0.77%)	⬆️

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[FlorentClarret]

Look good, just left one question 🙂