it takes more headshots than intended to kill a scrake with slashing weapons

credit goes to yeahiamcat for explaining this bug to me (hi)

category: code
reproducibility: always
summary: slashing weapons can't perform a "head blowing shot" to scrakes
description: slashing weapons don't kill a scrake when it has depleted a scrake's head health. the head health continues to go negative until the body health is 0, which is when the scrake dies.
example: as a level 21 berserker on HoE w/ 6 players, it takes 15 sawblade headshots to kill a scrake. but 6 sawblade headshots + 1 9mm pistol headshot would kill it too.
online/offline: both

edit: this happens with fleshpounds too

it takes more headshots than intended to kill a scrake with slashing weapons