Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Grafana Dashboard update for Prox Tests"
  - Grafana Dashboard update for Prox Tests

    JIRA: YARDSTICK-802

    Updated the Grafana dashboards to collect KPI's
    correctly & incorporate scale up changes in topology

    Influx-db stores the KPI’s fields as: <TG><Port><kpi>
    TG has changed from  : tg__1 to tg__0
    VNF has changed from : vnf__1 to vnf__0

    Change-Id: I3bd8be61210906bc4de95c9b1986033572d93277
    Signed-off-by: Abhijit Sinha <abhijit.sinha@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index d847fb6..def87da 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit d847fb62d92125f7be163375aa6a08f5a3b6f163
+Subproject commit def87da57962d932086840fc20950dc90de5c567