Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - [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>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index fdd8206..78b5a19 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit fdd8206d8f3d456fa3e3b56630e7449d55a71258
+Subproject commit 78b5a19e3071cbc080eeae0bdf22f5ab80c03180