Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'stable/danube'
  - Configure Yardstick flavor to give more RAM to ARM instances

    Yardstick TC005 fails with errors that indicate low memory conditions:
    "fio: error while loading shared libraries:
    librbd.so.1: cannot map zero-fill pages"
    Changing the yardstick flavor to give 1024MB of RAM instead of 512MB
    made this test case work.

    JIRA: ARMBAND-275

    Change-Id: I2193802082c28edb20004964d2df3780eb5eccb7
    Signed-off-by: Alexandru Nemes <alexandru.nemes@enea.com>
    (cherry picked from commit 5c8e38667e17059db1c62dd21f868966a6b2a519)