Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Proposing Jack Chan as a committer in Yardstick"
  - Proposing Jack Chan as a committer in Yardstick

    Jack Chan has contributed to the Yardstick project in many ways
    Achievements/Contributions include:
    - Kubernetes context
    - GUI
    - Yardstick API
    - Reporting fixes
    - Attending OPNFV Summit Beijing
    - Regularly attending Yardstick meetings

    Change-Id: Ie46a99619365893f3b877822f82f626cf7a36deb
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>