Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'stable/fraser'
  - nsb_setup: pin docker image version to release tag

    The install scripts pull tags for stable releases.

    We need to temporarily pin the image tag to the unreleased tag
    because we have to update the code before we actually tag the image.

    Or maybe we should make this a parameter to the script

    JIRA: YARDSTICK-1137

    Change-Id: I2e5f13ffe19d1c19fd7b8e071df28fd225be3d79
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>