A 20% fluff probability increases the precision of a spy connected to
every node by 10% on average, compared to a network using 0% fluff
probability. The current value (10% fluff) should increase precision by
~5% compared to baseline.
This decreases the expected stem length from 10 to 5. The embargo
timeout was therefore lowered to 39s; the fifth node in a stem is
expected to have a 90% chance of being the first to timeout, which is
the same probability we currently have with an expected stem length of
10 nodes.