Update hyperkube sync

Signed-off-by: Spyros Trigazis <spyridon.trigazis@cern.ch>

.gitlab-ci.yml

@@ -61,11 +61,11 @@ quay.io/coreos/prometheus-config-reloader_sync:
   script:
     - ./sync_image.sh "quay.io/coreos/prometheus-config-reloader:master"
 
-gcr.io/google-containers/hyperkube_sync:
+k8s.gcr.io/hyperkube_sync:
   stage: image_sync
   image: gitlab-registry.cern.ch/cloud/fedora-buildah:rawhide
   script:
-    - ./sync_image.sh "gcr.io/google-containers/hyperkube:v1.11.8"
+    - ./sync_image.sh "k8s.gcr.io/hyperkube:v1.18.8"
 
 k8s.gcr.io/etcd_sync:
   stage: image_sync