test: skip certain `xfail` tests that are causing tracebacks for now

[viniarck]

Closes #224

Summary

• Skipped certain xfail tests that are causing tracebacks for now, which are just false positive noise in the logs. Once validations are in place then this will be reverted (I'll map another issue shortly for this)

Local Tests

I made sure that of the tests was properly skipped

Ran 'hello' command on MongoDB successfully. It's ready!
+ python3 -m pytest tests/ -k test_035_patch_an_inconsistent_uni_a
============================= test session starts ==============================
platform linux -- Python 3.9.2, pytest-6.2.5, py-1.11.0, pluggy-1.0.0
rootdir: /tests
plugins: timeout-2.0.2
collected 227 items / 226 deselected / 1 selected

tests/test_e2e_13_mef_eline.py s                                         [100%]

=============================== warnings summary ===============================
usr/local/lib/python3.9/dist-packages/kytos/core/config.py:186
  /usr/local/lib/python3.9/dist-packages/kytos/core/config.py:186: UserWarning: Unknown arguments: ['tests/', '-k', 'test_035_patch_an_inconsistent_uni_a']
    warnings.warn(f"Unknown arguments: {unknown}")

-- Docs: https://docs.pytest.org/en/stable/warnings.html
------------------------------- start/stop times -------------------------------
================ 1 skipped, 226 deselected, 1 warning in 0.64s =================

End-to-End Tests

Not necessary to rerun the entire test suite since it's just skipping and there's no syntax errors

[viniarck]

Appreciated your review @gretelliz