Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Add a new runner to test end-to-end fast data path"
  - Add a new runner to test end-to-end fast data path

    This runner caters testing fast host data path (e.g. SRIOV) plus fast VM data path (VM running pktgen-dpdk).
    It is implemented as a new flavor of the existing Iteration runner.
    (1) Add a new SLA action rate-control
    (2) While the SLA target is not met, reduce packet rate until packet loss target is met.

    Change-Id: I633f391f1790f03ff31458458d79d3f272475ab5
    JIRA: YARDSTICK-615
    Signed-off-by: Jing Zhang <jing.c.zhang@nokia.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index bd877d6..af7518c 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit bd877d6bd6928ac4bdebdd292c15dc94241542f3
+Subproject commit af7518c51362ce882972c4b2168dbbfa4f5dcb2d