Update coreos-stable image

Our old coreos-stable image has docker 1.10

.gitlab-ci.yml

@@ -139,7 +139,7 @@ before_script:
 .coreos_calico_sep_variables: &coreos_calico_sep_variables
 # stage: deploy-gce-part1
   KUBE_NETWORK_PLUGIN: calico
-  CLOUD_IMAGE: coreos-stable
+  CLOUD_IMAGE: coreos-stable-1235-6-0-v20170111        
   CLOUD_REGION: us-west1-b
   CLUSTER_MODE: separated
   BOOTSTRAP_OS: coreos
@@ -176,7 +176,7 @@ before_script:
 .coreos_canal_variables: &coreos_canal_variables
 # stage: deploy-gce-part2
   KUBE_NETWORK_PLUGIN: canal
-  CLOUD_IMAGE: coreos-stable
+  CLOUD_IMAGE: coreos-stable-1235-6-0-v20170111
   CLOUD_REGION: us-east1-b
   CLUSTER_MODE: default
   BOOTSTRAP_OS: coreos