Update git submodules

* Update docs/submodules/yardstick from branch 'stable/danube'
  - Merge "fix bug: multi monitor" into stable/danube
  - fix bug: multi monitor

    JIRA: YARDSTICK-657

    Change-Id: I77223cc43d529828cf3f763529019590c35b2fcb
    Signed-off-by: HuanLi <lihuansse@tongji.edu.cn>
    (cherry picked from commit 67b56f734f1d2bb77601c2e75e29fd351f70498e)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 9a372b8..5bdc049 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 9a372b8adf618981e4fbfb8d0cb3a48674c65d92
+Subproject commit 5bdc049447e44738f8a0d67228906c07fd94821e