Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Create get_description and get_scenario_type for Scenario"
  - Create get_description and get_scenario_type for Scenario

    Created two new class functions for Scenario class:

    * "get_description" will return the first line of the docstring,
      if exists.
    * "get_scenario_type" will return the value of "__scenario_type__"
      variable.

    Change-Id: I8e3b47e33e0bae101b874c3975bb9c383397d188
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>