Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Resolve NameError in test_utils.py"
  - Resolve NameError in test_utils.py

    The import of the yardstick module was removed from test_util.py, which relied
    on this module location for a file name in
    test_import_modules_from_package_no_mod and test_import_modules_from_package.

    JIRA: YARDSTICK-1258
    Change-Id: I754dbadfb8d788236f354e9a0c1a61ad6c4abf70
    Signed-off-by: Emma Foley <emma.l.foley@intel.com>