Cancel Jenkins Queues and delete offline nodes

docker_instance_cleaner.groovy

import hudson.model.*
import jenkins.model.Jenkins

def q = Jenkins.instance.queue

q.items.findAll { it.task.name }.each { q.cancel(it.task) }

for (aSlave in hudson.model.Hudson.instance.slaves) {
    if (aSlave.getComputer().isOffline()  /* || aSlave.getComputer().isOnline()  */) { 
        aSlave.getComputer().setTemporarilyOffline(true,null);
        aSlave.getComputer().doDoDelete();
    }
}