net: dns: Avoid superfluous error message

If we have configured the DNS dispatcher to be only as a
responder but receive a query response, or if we are only
as a resolver but receive a query, then the dispatcher just
ignores the packet and returns -ENOENT.

Unfortunately we print an error message in this case

[00:10:18.818,000] <err> net_dns_dispatcher: DNS recv error (-2)

which is totally unnecessary and causes confusion so do not
print an error message in this case.

Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>