Fix Thread resolution client initialisation (ARMmbed#1915)

Check coap-service ID during initialisation to avoid badly
initialised object.

Author: Arto Kinnunen

source/6LoWPAN/Thread/thread_resolution_client.c

@@ -293,9 +293,14 @@ void thread_resolution_client_init(int8_t interface_id)
     this->interface_id = interface_id;
     this->notification_cb_ptr = NULL;
     this->error_cb_ptr = NULL;
-    ns_list_init(&this->queries);
     //TODO: Check if to use ephemeral port here
     this->coap_service_id = thread_management_server_service_id_get(interface_id);
+    if (this->coap_service_id < 0) {
+        tr_err("Thread resolution client init failed");
+        ns_dyn_mem_free(this);
+        return;
+    }
+    ns_list_init(&this->queries);
     ns_list_add_to_start(&instance_list, this);
 
     coap_service_register_uri(this->coap_service_id, THREAD_URI_ADDRESS_NOTIFICATION, COAP_SERVICE_ACCESS_POST_ALLOWED, thread_resolution_client_notification_post_cb);

source/6LoWPAN/Thread/thread_resolution_server.c

@@ -173,7 +173,7 @@ int thread_resolution_server_init(int8_t interface_id, thread_resolution_server_
     this->interface_id = interface_id;
     this->coap_service_id = thread_management_server_service_id_get(interface_id);
     if (this->coap_service_id < 0) {
-        tr_warn("Thread resolution srv init failed");
+        tr_err("Thread resolution srv init failed");
         ns_dyn_mem_free(this);
         return -3;
     }