Gnat's brain handles failing ACTIONS.INFEST in a fugly way

In brains/gnatbrain.lua:

-- THIS IS GROSS.. why does the "infest" DoAction not get it's OnFail event?!
brain:Stop()
brain:Start()

This is indeed gross, all that needs to be done is add a validfn to the BufferedAction:

      local ba = BufferedAction(inst, target, ACTIONS.INFEST)
      ba.validfn = function()
          local AGRO_STOP_DIST = 7
          return ba.doer:GetDistanceSqToInst(ba.target) <= AGRO_STOP_DIST * AGRO_STOP_DIST
      end
      return ba

This way, BufferedAction:IsValid would return false, causing LocoMotor component to reset action, no need to reset brain.