Do not ban peers for sending multiple valid requests (#8325)

We introduced banning of peers who spam us with the same request (more
than 2 times). However, we missed that it is completely legal to send
the same request multiple times as long as we did not provide any
answer. An example for that is the justification request. This request
is send multiple times until we could fetch the justification from one
of our peers. So, the solution to this problem is to tag requests as
fulfilled and to start counting these fulfilled requests. If the number
is higher than what we allow, the peer should be banned.