Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Create a sample lmbench test case base on kubernetes"
  - Create a sample lmbench test case base on kubernetes

    make samples/lmbench.yaml to support both Openstack and K8s
    with context_type specified. It defaultly use Heat context, if
    for k8s,
        yardstick -d task start samples/lmbench.yaml --task-args
        '{"context_type": "Kubernetes"}'

    JIRA: YARDSTICK-1310

    Change-Id: Ifa542e830fb5ab7823bd4f994ab5d7a8e8a5b415
    Signed-off-by: rexlee8776 <limingjiang@huawei.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 85b4cc5..d5df680 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 85b4cc5f7d9d4a53a58f117dbc133694e0abcbf3
+Subproject commit d5df680a4ccddd16a6434f47665062828630bfca