Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'stable/danube'
  - yardstick env influxdb/grafana cmd support centos

    JIRA: YARDSTICK-714

    Currently yardstick env influxdb/grafana command do not support centos.
    Because we use the gateway ip to get the service of influxdb and grafana.
    But in centos, we can not access influxdb/grafana service via gateway ip.
    In this patch, I use docker inspect to get the ip of influxdb and grafana.
    So these command can support centos.

    Change-Id: I4599cbbd0fe43de9cf08e5d9e74d31edbb742998
    Signed-off-by: chenjiankun <chenjiankun1@huawei.com>