Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - [userguide] Use literalinclude directive in 05-operation

    Uses literalinclude directive instead of having a copy of the file content in documentation.
    This means that any update to this file is detected, and the most up-to-date content is used.

    If a testcase is updated, the updates wil be picked up.
    The examples used are ones that are tested reqularly.

    JIRA: YARDSTICK-1066

    Change-Id: I15d967eb04d1e6f4348683d8746fa9989dceda94
    Signed-off-by: Emma Foley <emma.l.foley@intel.com>
  - [docs] update the user guide for "yardstick-operation"

    * Add a new chapter: operation which shows how to use Yardstick and
      how to create test cases
    * Include details on how to reuse and keep VNFs between testcases

    JIRA: YARDSTICK-885
    JIRA: YARDSTICK-886
    Change-Id: I365152e8812427a3c54259adbc18d5ddb216d775
    Signed-off-by: Emma Foley <emma.l.foley@intel.com>
  - [docs] Move user guide chapters to make room for new chapter.

    * Increment the numbering on chapters
    * Fix some of the changes flagged by doc8

    Change-Id: Ie03d165297671dfd50b9de339612cdc8bf00b988
    Signed-off-by: Emma Foley <emma.l.foley@intel.com>