Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Terminate openstack service process using kill command in HA test cases

    JIRA: YARDSTICK-659

    In some openstack environment, the service process cannot be killed by killall
    command but can be terminate by kill command.
    This patch is about to switch to use kill command in the
    fault_process_kill.bash to kill processes.

    Change-Id: Iec455ee56d3f31fb5c16de5994870d1acd33f41a
    Signed-off-by: JingLu5 <lvjing5@huawei.com>