Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Fix latency in l2 and l3 PROX generator config files"
  - Fix latency in l2 and l3 PROX generator config files

    JIRA: YARDSTICK-1211

    Change-Id: I0899d470ca5a0ec7d42d36a9ff9c39cc7369310c
    Signed-off-by: Xavier Simonart <xavier.simonart@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index e085b7e..a8468f9 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit e085b7ef9d01993531a1c484288333f371d041c4
+Subproject commit a8468f9aa6b55565b7d482bc8fdecfe7d9c07cb6