[metallb] Add variable for the metallb namespace (#11136)

roles/kubernetes-apps/metallb/templates/layer3.yaml.j2

@@ -9,7 +9,7 @@ apiVersion: metallb.io/v1beta1
 kind: Community
 metadata:
   name: "{{ community_name }}"
-  namespace: metallb-system
+  namespace: "{{ metallb_namespace }}"
 spec:
   communities:
   - name: "{{ community_name }}"
@@ -21,7 +21,7 @@ apiVersion: metallb.io/v1beta1
 kind: Community
 metadata:
   name: well-known
-  namespace: metallb-system
+  namespace: "{{ metallb_namespace }}"
 spec:
   communities:
   - name: no-export
@@ -51,7 +51,7 @@ apiVersion: metallb.io/v1beta1
 kind: BGPAdvertisement
 metadata:
   name: "{{ peer_name }}-local"
-  namespace: metallb-system
+  namespace: "{{ metallb_namespace }}"
 spec:
   aggregationLength: 32
   aggregationLengthV6: 128
@@ -70,7 +70,7 @@ apiVersion: metallb.io/v1beta1
 kind: BGPAdvertisement
 metadata:
   name: "{{ peer_name }}-external"
-  namespace: metallb-system
+  namespace: "{{ metallb_namespace }}"
 spec:
   {% if peer.aggregation_length is defined and peer.aggregation_length <= 30 %}
   aggregationLength: {{ peer.aggregation_length }}
@@ -93,7 +93,7 @@ apiVersion: metallb.io/v1beta2
 kind: BGPPeer
 metadata:
   name: "{{ peer_name }}"
-  namespace: metallb-system
+  namespace: "{{ metallb_namespace }}"
 spec:
   myASN: {{ peer.my_asn }}
   peerASN: {{ peer.peer_asn }}