Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - NSB NFVi PROX VPE losing many packets

    JIRA: YARDSTICK-1105

    Running a vPE test ends up with up to 25% drooped packets.
    This is due to tolerated loss being incorrectly configured,
    test duration was too short and test interval was too
    short.

    Note This is due to the fact that vPE use case have by
    default a tolerated loss of 100%, Now changed to 0.001,
    same as L2FWD

    Also: Grafan dashboard has been updated to show all SUT
    CPUS Utilization in 1 panel. And LINE rate MIN, MAX & TEST
    Rate have been added

    Change-Id: I7adae2199b3f656fe460705b6aeb3aa69c767d50
    Signed-off-by: Daniel Martin Buckley <daniel.m.buckley@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 8d3eedf..39b3d9a 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 8d3eedf007d338a032d106842cb66baa3a8eb8b7
+Subproject commit 39b3d9ae8ff19a0d64bff0e874f05b6dbcc30b01