Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Proposing Rodolfo Alonso Hernandez as a committer in Yardstick

    Rodolfo has contributed to Yardstick in many ways
    Achievement/Contributions include:
    - Userguide review and update
    - Provided high-quality code review comments.
    - Improved unittest code coverage
    - Improved code quality by fixing warnings and errors
    - Jenkins gate check improvements
    - Pip requirements checking and updating
    - Migration to Shade removing OpenStack project clients.
    - Regularly attending Yardstick meetings
    - JIRA personal dashboard:
      https://jira.opnfv.org/secure/Dashboard.jspa?selectPageId=11400
    - Contributions:
      https://gerrit.opnfv.org/gerrit/#/q/owner:rodolfo.alonso.hernandez%2540intel.com

    Change-Id: I3e5f14a3f99fffcd4bd4973aedc44ce4beeb22be
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>