Allow pre-downloaded images to be used effectively

According to http://kubernetes.io/docs/user-guide/images/ :
By default, the kubelet will try to pull each image from the
specified registry. However, if the imagePullPolicy property
of the container is set to IfNotPresent or Never, then a local\
image is used (preferentially or exclusively, respectively).

Use IfNotPresent value to allow images prepared by the download
role dependencies to be effectively used by kubelet without pull
errors resulting apps to stay blocked in PullBackOff/Error state
even when there are images on the localhost exist.

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

roles/kubernetes/node/templates/manifests/kube-proxy.manifest.j2

@@ -10,6 +10,7 @@ spec:
   containers:
   - name: kube-proxy
     image: {{ hyperkube_image_repo }}:{{ hyperkube_image_tag }}
+    imagePullPolicy: {{ k8s_image_pull_policy }}
     command:
     - /hyperkube
     - proxy

roles/kubernetes/node/templates/manifests/nginx-proxy.manifest.j2

@@ -10,6 +10,7 @@ spec:
   containers:
   - name: nginx-proxy
     image: {{ nginx_image_repo }}:{{ nginx_image_tag }}
+    imagePullPolicy: {{ k8s_image_pull_policy }}
     securityContext:
       privileged: true
     volumeMounts: