Update git submodules

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

    Removed unneeded output and stopped access to file system.

    JIRA: YARDSTICK-1271

    Change-Id: I15a58eb7bb81b69fe156433055f59a54372fa0a8
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 4faaadf..643d46a 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 4faaadf1de0936446935f31a54a8b5059747b265
+Subproject commit 643d46af0b97d18332ed2a87ec17313a4c2f8cb3