title: stop rufus-scheduler job from ruby script
body: <p>how can i stop rufus-scheduler from my script : </p>
  
  <pre><code>@scheduler = Rufus::Scheduler.new
  job = @scheduler.schedule_every '3m' do |job|
    # processing
  end
  job.call
  </code></pre>
  
  <p>I just want to test in first step if the job is running if true stop the job.
  Thanks</p>