message: Improve logging in upstream_policy
diff: @@ -81,12 +81,13 @@ expected<long> upstream_policy::add_path(strong_actor_ptr hdl,
  << CAF_ARG(downstream_credit));
  CAF_ASSERT(hdl != nullptr);
  if (!find(hdl)) {
  - CAF_LOG_DEBUG("add new upstraem path" << CAF_ARG(hdl));
  auto ptr = new upstream_path(std::move(hdl), sid, prio);
  paths_.emplace_back(ptr);
  assignment_vec_.emplace_back(ptr, 0);
  if (downstream_credit > 0)
  ptr->assigned_credit = std::min(max_credit_, downstream_credit);
  + CAF_LOG_DEBUG("add new upstraem path" << ptr->hdl
  + << "with initial credit" << ptr->assigned_credit);
  return ptr->assigned_credit;
  }
  return sec::upstream_already_exists;
  