Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "constants: cache YAML config values"
  - constants: cache YAML config values

    don't reparse the yardstick.yaml file each
    time we lookup an option.

    Since it is global data, just cache it in a global
    var

    Use pkg_resources.resource_filename
    to lookup the path of yardstick tests, intsead of using __file__

    pkg_resources is slightly more proper than __file__
    at least for packages

    Change-Id: I05d9748390a37bd45c53013fc084d23069ab7c51
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>