title: camel: use header value in multiple routes
body: <p>Is it possible to set a header in one route and then use it again later in another route in the same context?<br>
  For example, I have a route that sets a header as so:  </p>
  
  <pre><code>&lt;setHeader headerName="clientId"&gt;
     &lt;xpath&gt;/Alarm/clientid/text()&lt;/xpath&gt;
  &lt;/setHeader&gt;
  </code></pre>
  
  <p>The route uses Dead Letter Channel to send the message to an error route in the same context when delivery fails and I would like to use the clientId header I defined above in the message the error route sends, but currently calling the header returns nothing (an empty string I assume).</p>