Update git submodules

* Update docs/submodules/yardstick from branch 'stable/gambia'
  - Merge "[docs] Update the glossary" into stable/gambia
  - [docs] Update the glossary

    Add some new terms (OpenStack, Docker, PROX).

    JIRA: YARDSTICK-1335
    Change-Id: I948957cf7b1540f7a027ab9da2d829e5e05c87c8
    Signed-off-by: Emma Foley <emma.l.foley@intel.com>
    (cherry picked from commit 78b5a19e3071cbc080eeae0bdf22f5ab80c03180)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index a196a34..df0253c 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit a196a3437a8a465f183374b334439ec1dea7e03b
+Subproject commit df0253cd111e32f42498da6d9d1c3b351a8ce738