Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Heat: use pkey from string instead of key_filename"
  - Heat: use pkey from string instead of key_filename

    Instead of using a key_filename for Heat, we can
    read the key as a string directly using pkg_resources.resource_string()

    This will enable us to save Heat stacks as pod.yaml, because
    we can embedded the key into the pod.yaml directly.

    Change-Id: I16baaba17dab845ee0846f97678733bae33cb463
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>
    Signed-off-by: Edward MacGillivray <edward.s.macgillivray@intel.com>