Vulnerability detector test module refactor: test_scan_nvd_feed

[jmv74211]

It is asked to refactor the test module named test_scan_nvd_feed.py.

It is disabled for now, as it was failing or unstable, causing false positives.

Tasks

• Make a study of the objectives of the test, and what is being tested.
• Refactor the test. Clean and modularizable code.
• Check that the test always starts from the same state and restores it completely at the end of the test (independent of the tests previously executed in that environment).
• Review test documentation, and modify if necessary.
• Proven that tests pass when they have to pass.
• Proven that tests fail when they have to fail.
• Test in 5-10 rounds of execution that the test always shows the same result.
• Run all Vulnerability detector integration tests and check the "full green".

Checks

• The code complies with the standard PEP-8 format.
• Python codebase is documented following the Google Style for Python docstrings.
• The test is processed by qa-docs tool without errors.