Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Replace "python-heatclient" with "shade" client"
  - Replace "python-heatclient" with "shade" client

    Replaced "python-heatclient" with "shade" client. The "python-heatclient"
    library is removed from requirements file. "shade" client version 1.22.2
    is the required one for OpenStack Pike release.

    shade is the recommended client to interact with OpenStack clouds [1]

    [1] https://github.com/openstack-infra/shade

    JIRA: YARDSTICK-880

    Change-Id: Ibbdfc42a543d2d9ed4cf70d78de3de8cbecd0076
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>