The later members of the harvest_event structure are predictable and provide low value to the entropy pool. Only
feed in the relatively high entropy counter and explicit entropy buffer to increase measured input entropy.
See also:
https://people.freebsd.org/~jmg/vbsdcon_2017_ddfreebsdrng_slides.pdf
PR: 222807
Submitted by: W. Dean Freeman <badfilemagic AT gmail.com>
Obtained from: HBSD 8d809124d563937edd84c9c9d5494406e359c55c
Security: no -- low entropy marginal input has no known negative affect on pool quality