Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'stable/euphrates'
  - Bugfix: failed to generete gui files in stable/euphrates in CI

    JIRA: YARDSTICK-898

    Now the gui files failed to build in stable branch in CI.
    (local work, CI master work, CI stable not work).
    The reason is stable using ubuntu 14.04 and the nodejs version is 0.10.25.
    We need to update it.

    Change-Id: I15b9efb91eb6fc1e3245cf827c130d408034eae5
    Signed-off-by: chenjiankun <chenjiankun1@huawei.com>