Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Test case description and configuration file for yardstick_tc091:Control Node Openstack Service High Availability - Heat Api"
  - Test case description and configuration file for yardstick_tc091:Control
    Node Openstack Service High Availability - Heat Api

    JIRA: YARDSTICK-961

    Change-Id: I49fc2b2d8fc4fa090a74f1838f5ac386e39eaf49
    Signed-off-by: tjuyinkanglin <14_ykl@tongji.edu.cn>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 773ac34..612b711 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 773ac34dbd60a0e8b00d81bddbea23a1f4e39144
+Subproject commit 612b7112144dc689652e035131417fc0d8686b38