Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Cleanup TestIxLoadTrafficGen unit tests"
  - Cleanup TestIxLoadTrafficGen unit tests

    Removed unneeded output and mock system calls.

    JIRA: YARDSTICK-1270

    Change-Id: I0e04a67cab592216280481c7145188c4f9045466
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 9b18991..4faaadf 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 9b1899199dab5094374b8beda850af92e6f55491
+Subproject commit 4faaadf1de0936446935f31a54a8b5059747b265