Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Call core code directly in the API of run test case"
  - Call core code directly in the API of run test case

    JIRA: YARDSTICK-688

    We need to call core code directly in the API of runTestCase.
    It would be more stable.

    Change-Id: I431a85ded7cd3b20da0462f947c25d91bb99decd
    Signed-off-by: chenjiankun <chenjiankun1@huawei.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 8996240..9ba594f 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 8996240be14d6f7979a6ae02dd474b03d50e79d9
+Subproject commit 9ba594fa3f34d551d34abd7582281ce081924c67