jenkins: run jobs as root

reference: https://stackoverflow.com/questions/29926773/run-shell-command-in-jenkins-as-root-user

1. sudo vi /etc/default/jenkins

2. $JENKINS_USER="root"

3. sudo chown -R root:root /var/lib/jenkins

   sudo chown -R root:root /var/cache/jenkins

   sudo chown -R root:root /var/log/jenkins

4. service jenkins restart ps -ef | grep jenkins