If Modified Since delay is too long when V3AuthVotingInterval is very short
Clients add 3 minutes to the last consensus valid after time to create an "If Modified Since" header. This works when MIN_VOTE_INTERVAL is 5 minutes.
But when the V3AuthVotingInterval is set lower in a testing network (see #13823 (moved) and #13718 (moved)), 3 minutes can be far too long to wait for an updated consensus. (For example, MIN_VOTE_INTERVAL_TESTING is 10 seconds.)
I'd like to set the "If Modified Since" header to halfway between the valid after and fresh until times, but only when the V3AuthVotingInterval is particularly short (less than 6 minutes).
By comparison, the default of 3 minutes is 1/20 the default consensus interval of 60 minutes.