fix two bugs: 1.leader lost again 2.`http.Server` can not be closed immediately via `Close` method
fix two bugs: 1.leader lost again 2.`http.Server` can not be closed immediately via `Close` method

bbklab/swan,Dataman-Cloud/swan,pwzgorilla/swan,pwzgorilla/swan,xiaods/swan,bbklab/swan,Dataman-Cloud/swan,xiaods/swan