Lower-bound the log approximation and stop using it > ~98.5%

Lower-bound the log approximation and stop using it > ~98.5%

When we start getting a numerator and divisor particularly close to
each other, the log approximation starts to get very noisy. In
order to avoid applying scores that are basically noise (and can
range upwards of 2x the default per-hop penalty), simply consider
such cases as having a success probability of 100%.