Jenkins の再起動方法です。
http://<jenkins.server>/restart
http://<jenkins.server>/safeRestart
http://<jenkins.server>/exit
http://<jenkins.server>/safeExit
http://<jenkins.server>/quietDown
http://<jenkins.server>/cancelQuietDown
https://cloudbees.zendesk.com/hc/en-us/articles/216118748-How-to-Start-Stop-or-Restart-your-Instance