When Jenkins is started as a service and the restart is done from web page Jenkins PID is changed, but in
/var/run/jenkins.pid remains the old one, which make problem e.g. when stopping Jenkins.
1. install jenkins from rpm
2. run service jenkins start
3. restart Jenkins from the UI (e.g. after plugin installation)
4. run service jenkins stop / check Jenkins PID and compare with PID in /var/run/jenkins.pid