title: Rails 6 & deliver_later doesn't affect ActionMailer::Base.deliveries
body: <p>After upgrading to Rails 6 I am noticing that default mailer's <code>.deliver_later</code> is not working the same as in Rails 5. </p>
  
  <p>Configuration: </p>
  
  <pre><code>config.active_job.queue_adapter = :inline
  </code></pre>
  
  <p>When running <code>Mailer.register_email(...).deliver_later</code> - nothing is stored in <code>ActionMailer::Base.deliveries</code>. This array gets filled if I run <code>perform_enqueued_jobs</code> - it seams like <code>queue_adapter = :inline</code> doesn't work the way I expect it to work. </p>
  
  <p>If I run <code>Mailer.send(...).deliver_now</code> then <code>ActionMailer::Base.deliveries</code> has proper value in it.</p>
  
  <p>Any idea why this is happening and how to solve this?  </p>