resolved: change error code when trying to resolve direct LLMNR PTR RRs

If we try to resoolve an LLMNR PTR RR we shall connect via TCP directly
to the specified IP address. We already refuse to do this if the address
to resolve is of a different address family as the transaction's scope.
The error returned was EAFNOSUPPORT. Let's change this to ESRCH which is
how we indicate "not server available" when connecting for LLMNR or DNS,
since that's what this really is: we have no server we could connect to
in this address family.

This allows us to ensure that no server errors are always handled the same
way.

src/resolve/resolved-dns-transaction.c

@@ -284,7 +284,7 @@ static int dns_transaction_open_tcp(DnsTransaction *t) {
                         if (r == 0)
                                 return -EINVAL;
                         if (family != t->scope->family)
-                                return -EAFNOSUPPORT;
+                                return -ESRCH;
 
                         fd = dns_scope_tcp_socket(t->scope, family, &address, LLMNR_PORT, NULL);
                 }