view: change to a more natural semantics

I think it makes more sense. Real-life example: https://lists.nic.cz/pipermail/knot-resolver-users/2018/000081.html

I tested the change briefly on that example (in addition to the deckard test we had).

modules/policy/policy.lua

@@ -549,12 +549,18 @@ end
 -- as a dependency chain, e.g. r1,r2,r3 -> r3(r2(r1(state)))
 policy.layer = {
 	begin = function(state, req)
+		-- Don't act on "resolved" cases.
+		if bit.band(state, bit.bor(kres.FAIL, kres.DONE)) ~= 0 then return state end
+
 		req = kres.request_t(req)
 		return policy.evaluate(policy.rules, req, req:current(), state) or
 		       policy.evaluate(policy.special_names, req, req:current(), state) or
 		       state
 	end,
 	finish = function(state, req)
+		-- Don't act on "resolved" cases.
+		if bit.band(state, bit.bor(kres.FAIL, kres.DONE)) ~= 0 then return state end
+
 		req = kres.request_t(req)
 		return policy.evaluate(policy.postrules, req, req:current(), state) or state
 	end