Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - test_vpe_vnf: speedup unittest, mock time

    Change-Id: I046fae81c23555573df7d9e2e80995499062cf38
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 49d3585..9b85639 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 49d358550209ab39bf618d8b226f655a0b54d13f
+Subproject commit 9b8563948c561d11de44cb6668f6c5c6641562ac