Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Clean functional tests in "test_cli_scenario""
  - Clean functional tests in "test_cli_scenario"

    Changed how "test_cli_scenario" tests check the presence
    of a string.

    Fixed "test_scenario_show_Lmbench": logic in [1] was incorrectly
    assigning an string value instead of the result of the "in"
    clause.

    [1] https://github.com/opnfv/yardstick/blob/stable/euphrates/tests/functional/test_cli_scenario.py#L35-L36

    Change-Id: I71fceabad972e4c0d9e78cbfeb85dcd6a5ae4bda
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>