Add phase to apply CNI (capd)

* add phase initinfra-networking-target
  to apply CNI

Relates-To: #452
Change-Id: I239de9d3cecb6da66a8f06ebc7bd93def9cdacee

manifests/site/docker-test-site/phases/plan.yaml

@@ -5,6 +5,7 @@ metadata:
 phases:
   - name: clusterctl-init-ephemeral
   - name: controlplane-ephemeral
+  - name: initinfra-networking-target
   - name: clusterctl-init-target
   - name: clusterctl-move
   - name: workers-target

manifests/site/docker-test-site/target/initinfra-networking/kustomization.yaml

@@ -0,0 +1,6 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+resources:
+  - ../../../../composite/infra
+commonLabels:
+  airshipit.org/stage: initinfra