web_connectivity: blocking key is set to false, while it should be set to dns

[hellais]

In the following measurement: https://explorer.ooni.org/measurement/20220808T164350Z_webconnectivity_ID_17995_n1_7PEtlgE9r63GDkKU?input=http://xhamster.com

the value of the test_keys are:

"dns_consistency": "inconsistent"
"blocking": false

while it should have marked it as blocking: true

[bassosimone]

The issue is that the DNS inconsistency is basically not used by Web Connectivity. There is a tussle between DNS heuristics and HTTP heuristics. In this case, the DNS heuristics are correct and the HTTP ones incorrect.

While I was working on the latest websteps prototype, we discussed with issue with @hellais and agreed it's quite fundamental to the whole model of Web Connectivity and we were unsure whether changing it.

The really fundamental flaw here is the split between measurement gathering and scoring inside the probe, which should go away when we rewrite the experiment in a step-by-step style.