跟进问题，实际错误是获取update-center.json更新超时
目前代码写死了
https://github.com/jenkinsci/jenkins/blob/04b46d1c68513e4a105b5acdfb7534c89da94eea/war/src/main/js/api/pluginManager.js#L64

// default 10 seconds for AJAX responses to return before triggering an error condition
var pluginManagerErrorTimeoutMillis = 10 * 1000;

解决方法

动态调试，将pluginManagerErrorTimeoutMillis增加100倍，然后继续