Update git submodules

* Update docs/submodules/yardstick from branch 'stable/gambia'
  - Merge changes Ia8783de8,I61421095 into stable/gambia

    * changes:
      Update: Trex KPI not collected no rabbitmq user
      Trex KPI are not collected due to rabbitmq user

  - Update: Trex KPI not collected no rabbitmq user

    Update of review #63707: missed yardstick password hash.
    This must be set on top of changes on review.

    JIRA: YARDSTICK-1479

    Change-Id: Ia8783de81ad91ea7421c6bbff87a30c59db2d44c
    Signed-off-by: Stepan Andrushko <stepanx.andrushko@intel.com>
  - Trex KPI are not collected due to rabbitmq user

    Changed the way rabbitmq-server user is created. Fix is needed to
    collect KPIs from Trex.

    JIRA: YARDSTICK-1479

    Change-Id: I6142109563fcdb27e0ec554dd08567a1a43237e7
    (cherry picked from commit d06e6da19db545dfcc6fdfdc706b9cccdb75c498)
    formerly: I54369535fdb7af6af76de30f758227736f83db78
    Signed-off-by: Stepan Andrushko <stepanx.andrushko@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 5b77ebe..7d4c4b6 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 5b77ebed3fd8b4a86a726feedcc3fc42e8855fdb
+Subproject commit 7d4c4b6d08209b8365854c28f5e4e8e53c6a5a6c