Ticket 13640

i took a look at 13640, here is a proposal to fix it: https://github.com/olliwolli/ooni-pipeline/commit/39afda26d48f092b08f4a8479053c0e65b048d8b . I didn't find any check to make sure that the control and experiment measurements actually are for the same bridge based on a hash. The code only checks if the time is is close. Maybe I overlooked something or this is intentional?