CID 486476: Memory - corruptions (OVERRUN) in lib/dns/resconf.c

After 371defc3, Coverity Scan claims memory corruption in lib/dns/resconf.c:

/lib/dns/resconf.c: 246 in add_server()
240     
241     		/* XXX: special case: treat all-0 IPv4 address as loopback */
242     		v4 = &((struct sockaddr_in *)res->ai_addr)->sin_addr;
243     		if (memcmp(v4, zeroaddress, 4) == 0) {
244     			memmove(v4, loopaddress, 4);
245     		}
>>>     CID 486476:  Memory - corruptions  (OVERRUN)
>>>     Overrunning struct type sockaddr_in of 16 bytes by passing it to a function which accesses it at byte offset 27 using argument "res->ai_addrlen" (which evaluates to 28). [Note: The source code implementation of the function has been overridden by a builtin model.]
246     		memmove(&address->type.sin, res->ai_addr, res->ai_addrlen);
247     	} else if (res->ai_family == AF_INET6) {
248     		memmove(&address->type.sin6, res->ai_addr, res->ai_addrlen);
249     	} else {
250     		isc_mem_put(mctx, address, sizeof(*address));
251     		UNEXPECTED_ERROR("ai_family (%d) not INET nor INET6",