Update git submodules

* Update docs/submodules/multicloud/k8s.git from branch 'master'
  to 6acebe1cc8bc16fc4d99ca8279a989b624b85375
  - Merge "Switch to xenial Docker image"
  - Switch to xenial Docker image

    The Ubuntu Xenial Docker image has lower footprint than Trusty,
    besides more security patches. This change modifies the Dockerfile
    that is used for building the Docker image.

    Change-Id: I89228ef555668aad1e621973fd33481ce49499d3
    Signed-off-by: Victor Morales <victor.morales@intel.com>
    Issue-ID: MULTICLOUD-301

diff --git a/docs/submodules/multicloud/k8s.git b/docs/submodules/multicloud/k8s.git
index e35591a..6acebe1 160000 (submodule)
--- a/docs/submodules/multicloud/k8s.git
+++ b/docs/submodules/multicloud/k8s.git
@@ -1 +1 @@
-Subproject commit e35591ab0994f19ca86e96d28fe77041bcb3a9f1
+Subproject commit 6acebe1cc8bc16fc4d99ca8279a989b624b85375