fix tolerations invalid YAML if undefined

roles/kubernetes-apps/metrics_server/templates/metrics-server-deployment.yaml.j2

@@ -84,6 +84,7 @@ spec:
       volumes:
         - name: tmp
           emptyDir: {}
+{% if not masters_are_not_tainted or metrics_server_extra_tolerations is defined %}
       tolerations:
 {% if not masters_are_not_tainted %}
         - key: node-role.kubernetes.io/master
@@ -93,6 +94,7 @@ spec:
 {% endif %}
 {% if metrics_server_extra_tolerations is defined %}
         {{ metrics_server_extra_tolerations | list | to_nice_yaml(indent=2) | indent(8) }}
+{% endif %}
 {% endif %}
       affinity:
         podAntiAffinity:
@@ -111,7 +113,7 @@ spec:
 {% if metrics_server_extra_affinity is defined %}
         {{ metrics_server_extra_affinity | to_nice_yaml | indent(width=8) }}
 {% endif %}
-{% if metrics_server_nodeselector %}
+{% if metrics_server_nodeselector is defined %}
       nodeSelector:
         {{ metrics_server_nodeselector | to_nice_yaml | indent(width=8) }}
 {% endif %}