Fix cilium operator metrics activation (#8000) (#8033)

This is a cherry-pick of 598f178054

Co-authored-by: Léopold Jacquot <leopold.jacquot@infomaniak.com>

roles/network_plugin/cilium/templates/cilium-config.yml.j2

@@ -38,6 +38,8 @@ data:
   # scheduled.
 {% if cilium_enable_prometheus %}
   prometheus-serve-addr: ":9090"
+  operator-prometheus-serve-addr: ":6942"
+  enable-metrics: "true"
 {% endif %}
 
   # If you want to run cilium in debug mode change this value to true