Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'stable/euphrates'
  - Update load_images.sh to MCP@aarch64

    The load_images.sh script still contained old functionality.
    The changes are:
    - don't use TestVM anymore, MCP does not load that by default like Fuel did
      upload the cirros image instead
    - don't upload the kernel separately for aarch64, one part image works now
    - add the needed extra-properties accordingly to each image

    The script was tested on arm, the test are running now without errors

    JIRA: ARMBAND-285

    Change-Id: Iee8ce6cde43bebceb2edbb1310ea81c665876aff
    Signed-off-by: Cristina Pauna <cristina.pauna@enea.com>
    (cherry picked from commit af71c468fe83a5149e0e18cdb233e059302209e3)