Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Change endpoint to url in API

    There are come conflict with new architecture.
    Also it is more proper to use url as endpoint.

    Change-Id: Idce331e36d85d0720bbf3255dca29ba6022e18b2
    Signed-off-by: chenjiankun <chenjiankun1@huawei.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 29484c3..b6d8765 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 29484c3071028df6c897797706117082a4b8c3f5
+Subproject commit b6d8765f2acbeefeb8e8f756b2243e8bac2a06b6