fix: honor libvirt network config, preserve DHCP DNS with search-only NM config, and exact-match Xen VM names

roles/virtualization/tasks/xen.yml

@@ -74,4 +74,6 @@
         virtualization_vm_created_in_run: true
       when:
         - virtualization_xen_list_result is defined
-        - hostname in virtualization_xen_list_result.stdout
+        - >-
+          virtualization_xen_list_result.stdout | default('')
+          is search('(?m)^' ~ (hostname | ansible.builtin.regex_escape) ~ '\\s+\\d+\\s')

roles/virtualization/templates/vm.xml.j2

@@ -48,7 +48,7 @@
     {% endif %}
     <interface type='network'>
       <mac address="{{ virtualization_mac_address }}"/>
-      <source network='default'/>
+      <source network='{{ system_cfg.network if (system_cfg.network | default('' ) | string | length) > 0 else "default" }}'/>
       <model type='virtio'/>
     </interface>
     {% if virtualization_tpm2_enabled %}