Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "testcase start service script fail on centos env"
  - testcase start service script fail on centos env

    JIRA: YARDSTICK-676

    In the HA test cases, script 'start_serice.bash' is used to restart the OpenStack service to recover killed process.
    It uses 'lsb_release' command to determine the host linux distribution and the target Openstack service name.
    In some environments, the 'lsb_release' is not installed hence will cause process-recovery failure.

    This patch states the software precondions in the HA test case descriptions.

    Change-Id: Ie3f503b8185deec13eebbcacbeac57c0a018cb73
    Signed-off-by: JingLu5 <lvjing5@huawei.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 6719224..7d3d225 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 6719224ad22d616cb0dbae2fcc47873acfc6dbf4
+Subproject commit 7d3d2250ee6bb2b66bf8c5beda20c737abb57484