mdns: Fix parsing answers with questions when instance name not set

mdns resolver didn't correctly resolved queries when host name wasn't
assigned. Fixed by allowing processing also if some answer present
(non-strict mode)

Closes https://github.com/espressif/esp-idf/issues/6598

components/mdns/mdns.c

@@ -2676,7 +2676,7 @@ void mdns_parse_packet(mdns_rx_packet_t * packet)
     }
 
     //if we have not set the hostname, we can not answer questions
-    if (header.questions && _str_null_or_empty(_mdns_server->hostname)) {
+    if (header.questions && !header.answers && _str_null_or_empty(_mdns_server->hostname)) {
         free(parsed_packet);
         return;
     }