Update git submodules

* Update docs/submodules/yardstick from branch 'stable/gambia'
  - Merge "Trex KPI are not collected due to rabbitmq user" into stable/gambia
  - 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: I54369535fdb7af6af76de30f758227736f83db78
    Signed-off-by: Stepan Andrushko <stepanx.andrushko@intel.com>
    (cherry picked from commit d06e6da19db545dfcc6fdfdc706b9cccdb75c498)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index e17ba5d..3f19983 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit e17ba5d730878ae2a92cc9130e47630cc6745d91
+Subproject commit 3f1998305fec2261729260fd1954cf6fea9fc9e0