lua: ensure answer_clear() keeps original EDNS

Answers to EDNS requests from certain lua policies that use the answer_clear() function would lack OPT RR and thus violate the MUST condition in RFC6891.6.1.1.

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Fixes #657 (closed)

daemon/lua/kres-gen-29.lua

@@ -378,6 +378,7 @@ int knot_pkt_put_rotate(knot_pkt_t *, uint16_t, const knot_rrset_t *, uint16_t,
 knot_pkt_t *knot_pkt_new(void *, uint16_t, knot_mm_t *);
 void knot_pkt_free(knot_pkt_t *);
 int knot_pkt_parse(knot_pkt_t *, unsigned int);
+knot_rrset_t *kr_request_ensure_edns(struct kr_request *);
 knot_pkt_t *kr_request_ensure_answer(struct kr_request *);
 struct kr_rplan *kr_resolve_plan(struct kr_request *);
 knot_mm_t *kr_resolve_pool(struct kr_request *);