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)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 9f576f2..f9e3847 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 9f576f22b8233f4baea14e42786c1a07f8afecd9
+Subproject commit f9e384775559bca42e25f2f0ee952e2e304e678b