Add xml header to the proxy template

[marek130]

Fixing problem of xml header. Restarting Jenkins service is adding this header.

Pull Request (PR) description

There is no possible to achieve the desired state by Puppet because the content of proxy.xml file is missing the XML header.
After restarting the Jenkins service the header is added automatically. So, there is a fight between the proxy template and Jenkins service.

Notice: /Stage[main]/Jenkins::Proxy/File[/var/lib/jenkins/proxy.xml]/content:
--- /var/lib/jenkins/proxy.xml  2023-10-10 09:34:29.396190879 +0200
+++ /tmp/puppet-file20231010-27492-128ipzr      2023-10-10 09:36:37.746168509 +0200
@@ -1,5 +1,4 @@
-<?xml version='1.1' encoding='UTF-8'?>
 <proxy>
   <name>company.com</name>
   <port>9443</port>
-</proxy>
\ No newline at end of file
+</proxy>

[ekohl]

Looking at the diff, it still wouldn't be idempotent since there is no line ending in the generated version while this template does. I wonder what the best way to achieve that is, because many tools actually try hard to ensure that.