Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "vnfdgen: replace yaml.load with yaml.safe_load"
  - vnfdgen: replace yaml.load with yaml.safe_load

    JIRA: YARDSTICK-760

    Change-Id: I145c948c1f08562e12877f5d0fe7e797e9d989f9
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index ac4f505..d35ed0f 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit ac4f5055109dff03f9f1bf6ab42a27cd78446d92
+Subproject commit d35ed0fb93098162af4e925d8499554510f73d10