code: boolean isAsync() {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.entry(this, tc, "isAsync");
          boolean isAsync = !asyncConsumers.isEmpty() && getState() == STARTED;
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.exit(this, tc, "isAsync", isAsync);
          return isAsync;
      }
docs: Test to see if any of the consumers of this session are using
  async message delivery.
  
  @return true if the session is being used for async delivery