Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "cleanup: remove fuel plugin since fuel@opnfv uses mcp"
  - cleanup: remove fuel plugin since fuel@opnfv uses mcp

    Change-Id: Ic9fb9db5c5af517cec1e60740ce5a8fe0572c5bf
    Signed-off-by: Guo Ruijing <ruijing.guo@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 418b310..bbd60b6 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 418b31051fb38881e3f18ad93d036878297e8ad7
+Subproject commit bbd60b6bddcf363d76c1dff34d21158caa18c0a1