Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Bugfix: docker build failed

    Due to no inventory.ini specified in Dockerfile, which
    resulsts in ansible-playbook run fail

    JIRA: YARDSTICK-1277

    Change-Id: Iaf689b71b8c86b54b2451d8a8c480f7d94d53561
    Signed-off-by: rexlee8776 <limingjiang@huawei.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index f6c837f..ce9a39a 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit f6c837fbaa0000c2749666e9b8fb092a26a7e0f3
+Subproject commit ce9a39a0e9e2747afa722f360ddc74dc697b3217