Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Add intermediate variable for HA test"
  - Add intermediate variable for HA test

    JIRA: YARDSTICK-397

    Change-Id: I3489893caa5b8194b63cb844325ec0b2c554aecc
    Signed-off-by: qiujuan <juan_qiu@tongji.edu.cn>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 3a87a32..ac4f505 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 3a87a3262b5aefb7231f90a3b3808b947353eca5
+Subproject commit ac4f5055109dff03f9f1bf6ab42a27cd78446d92