use only UA_malloc internally

src/server/ua_subscription.c

@@ -466,7 +466,7 @@ void UA_Subscription_publishCallback(UA_Server *server, UA_Subscription *sub) {
     UA_NotificationMessageEntry *retransmission = NULL;
     if(notifications > 0) {
         /* Allocate the retransmission entry */
-        retransmission = malloc(sizeof(UA_NotificationMessageEntry));
+        retransmission = UA_malloc(sizeof(UA_NotificationMessageEntry));
         if(!retransmission) {
             UA_LOG_WARNING_SESSION(server->config.logger, sub->session,
                                    "Subscription %u | Could not allocate memory "