Bump docker to 1.13.1 for k8s clusters.

Change-Id: I72e2a0792b561b3a156543b7b782d4e62f863aec
diff --git a/classes/cluster/sl-k8s-contrail/kubernetes/compute.yml b/classes/cluster/sl-k8s-contrail/kubernetes/compute.yml
index 03890c1..61b80e1 100644
--- a/classes/cluster/sl-k8s-contrail/kubernetes/compute.yml
+++ b/classes/cluster/sl-k8s-contrail/kubernetes/compute.yml
@@ -27,7 +27,7 @@
   docker:
     host:
       pkgs:
-        - docker-engine=1.12.6-0~ubuntu-xenial
+        - docker-engine=1.13.1-0~ubuntu-xenial
         - python-docker
   kubernetes:
     pool: