Update git submodules

* Update docs/submodules/yardstick from branch 'stable/gambia'
  - Merge "Add traffic duration support in test case" into stable/gambia
  - Add traffic duration support in test case

    Implement code to support traffic_duration field in test case options.
    This updates the 'duration' in Landslide session profile.
    traffic_duration should always be much less than runner duration/timeout.

    JIRA: YARDSTICK-1427

    Change-Id: I51094bade683ca8758136ccb619e8894a2ecef72
    Signed-off-by: Orest Voznyy <orestx.voznyy@intel.com>
    (cherry picked from commit ae2ceba66519555749c67eefe2170ea716a1411b)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 3f19983..b09b9dd 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 3f1998305fec2261729260fd1954cf6fea9fc9e0
+Subproject commit b09b9dd3d55a489620f9bb129eb2ddde49009b56