Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Use context name instead of key_uuid"
  - Use context name instead of key_uuid

    context.key_uuid is only used as a suffix for the key files.
    There is already a unique ID associated with a the context;
    the context name includes a task ID, which is a UUID.

    This patch sets context.key_uuid to to context.name instead of
    generating a separate UUID

    As a result, get_short_key_uuid() is not needed.

    JIRA: YARDSTICK-1028
    Change-Id: Id175061d6cfe23a068bb3d12ce176c1f176e8236
    Signed-off-by: Emma Foley <emma.l.foley@intel.com>