Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'stable/danube'
  - pip install yardstick failed in Apex

    JIRA: YARDSTICK-625

    In Apex, yardstick uninstall and install via pip failed.
    This bug blocks yardstick CI jobs.
    This patch enables pip install yardstick in editable mode.
    So the install_yardstick() in yardstick_verify is unnecessary.

    Change-Id: If290dac5fee5584601064ae9753ae2340643d3ca
    Signed-off-by: JingLu5 <lvjing5@huawei.com>
    (cherry picked from commit d2cb7ce7331d8da4c3b5b70b09dac49cf65d1710)