Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Create Dockerfile to create a yardstick-image of docker"
  - Create Dockerfile to create a yardstick-image of docker

    this Dockerfile target to generate a image with testing tool
    installed, similar to yardstick-image for VM. The docker image
    is used by k8s to start pods and test.

    JIRA: YARDSTICK-1287

    Change-Id: Id09a3fb6d880869c8f523d688b2ef641fb434541
    Signed-off-by: rexlee8776 <limingjiang@huawei.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 5b37f2e..caee6b2 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 5b37f2eb188c390ce6942940e0ad9f33900dafd5
+Subproject commit caee6b2a603388c02e961582d78244a2e9e98372