Option for MetalLB to talk BGP (#6383)

* Option for MetalLB to talk BGP

* Check for BGP peers when metallb_protocol is bgp

* README clarification

* Commented values as documentation only in the sample inventory

* layer 2 or BGP, not both

roles/kubernetes-apps/metallb/templates/metallb-config.yml.j2

@@ -6,6 +6,14 @@ metadata:
   name: config
 data:
   config: |
+{% if metallb_protocol == 'bgp' %}
+    peers:
+{% for peer in metallb_peers %}
+    - peer-address: {{ peer.peer_address }}
+      peer-asn: {{ peer.peer_asn }}
+      my-asn: {{ peer.my_asn }}
+{% endfor %}
+{% endif %}
     address-pools:
     - name: loadbalanced
       protocol: {{ metallb_protocol }}