getnameinfo: fix calling __dns_parse with potentially too large rlen

__res_send returns the full answer length even if it didn't fit the
buffer, but __dns_parse expects the length of the filled part of the
buffer.

This is analogous to commit 77327ed064bd57b0e1865cd0e0364057ff4a53b4,
which fixed the only other __dns_parse call site.

src/network/getnameinfo.c

@@ -162,8 +162,10 @@ int getnameinfo(const struct sockaddr *restrict sa, socklen_t sl,
 			query[3] = 0; /* don't need AD flag */
 			int rlen = __res_send(query, qlen, reply, sizeof reply);
 			buf[0] = 0;
-			if (rlen > 0)
+			if (rlen > 0) {
+				if (rlen > sizeof reply) rlen = sizeof reply;
 				__dns_parse(reply, rlen, dns_parse_callback, buf);
+			}
 		}
 		if (!*buf) {
 			if (flags & NI_NAMEREQD) return EAI_NONAME;