Switch linaro-us cloud to ipv6 only

There are insufficient ipv4 floating-ips to cover our VM quota; switch
to ipv6 only so all vm's can boot.

Change-Id: I2225fa9ea888bcf167be7139e036a4b5406b1f4f

playbooks/templates/clouds/nodepool_clouds.yaml.j2

@@ -108,7 +108,13 @@ clouds:
       user_domain_name: default
   linaro-us:
     regions:
-      - RegionOne
+      - name: RegionOne
+        values:
+          networks:
+            - name: "os-jobs-network"
+              routes_externally: false
+              routes_ipv6_externally: true
+              nat_destination: true
     identity_api_version: '3'
     auth:
       auth_url: https://us.linaro.cloud:5000
@@ -117,6 +123,7 @@ clouds:
       project_name: '{{ nodepool_linaro_us_project }}'
       project_domain_name: default
       user_domain_name: default
+    floating_ip_source: None
   limestone:
     regions:
       - name: RegionOne