Evaluate notary results to see if quorum is achieved after each notary response

[danwent]

This would mean that if a notary server was down but not needed for quorum, the process of querying notaries could end after sufficient results were returned without waiting for the notary query timeout to expire.

In theory, this should also let us increase the timeout, as it would only have an impact when the results where actually relevant to a decision. This would likely help on-demand probes succeed more often.