message: [dnssd] fix printing string after its destruction
diff: @@ -157,13 +157,13 @@ void DiscoveryProxy::OnDiscoveryProxyUnsubscribe(const char *aFullName)
  subscription.mSubscriptionCount--;
  assert(subscription.mSubscriptionCount >= 0);
  + otbrLogDebug("service subscriptions: %sx%d", it->ToString().c_str(), it->mSubscriptionCount);
  +
  if (subscription.mSubscriptionCount == 0)
  {
  mSubscriptions.erase(it);
  }
  - otbrLogDebug("service subscriptions: %sx%d", it->ToString().c_str(), it->mSubscriptionCount);
  -
  if (GetServiceSubscriptionCount(nameInfo.mInstanceName, nameInfo.mServiceName, nameInfo.mHostName) == 0)
  {
  if (subscription.mHostName.empty())
  