Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Make context types constants"
  - Make context types constants

    Make context types constants. These are the current context types:
      - Dummy
      - Heat
      - Kubernetes
      - Node
      - StandaloneOvsDpdk
      - StandaloneSriov

    Any reference to a context type should use the referred constant.

    JIRA: YARDSTICK-1292

    Change-Id: I1ff0085161f88304d71e3ddad7975f9020e0fc20
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index bdd301b..c35fe95 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit bdd301b4b59fffc44d99ca2a631d9d8a81efdfa2
+Subproject commit c35fe95566156f9bec4c516f6e0cd9c79c96a492