Update git submodules

* Update docs/submodules/yardstick from branch 'stable/fraser'
  - Merge "Refactor RFC2455 TRex traffic profile injection" into stable/fraser
  - Refactor RFC2455 TRex traffic profile injection

    The TRex RFC2455 traffic profile configures the duration of the traffic
    injection. Once the traffic is started, the traffic profile should poll
    the traffic injector client for the injection status. When the injection
    is finished, the traffic execution should end.

    Instead of this, the traffic profile waits a fixed time (using time.sleep
    method) and then stops the traffic. This approach is not accurate and may
    cause shorter injection periods.

    JIRA: YARDSTICK-1197

    Change-Id: I5090df81ef4ec7945ff6c1aff070656b48e0fe77
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>
    (cherry picked from commit 340be73be5fd20067c23a7ddce9073639e355d3a)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 413b936..18657d0 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 413b936c22e6b581ac25cec581a60bc7bb73b1b4
+Subproject commit 18657d0ffc9cbc46a17f1a15cc8e884b1124ebbc