Update git submodules

* Update docs/submodules/yardstick from branch 'stable/euphrates'
  - bugfix: remove pod_name in host and unify host parameter

    for none-ha test case, use host to be parameter
    for ha test case, use attack_host as parameter

    Change-Id: I053df00adab17814dd54584a1ae081548163dc68
    Signed-off-by: rexlee8776 <limingjiang@huawei.com>
    (cherry picked from commit 18b2c357c3d281fbdf5261958ef60abb98915486)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index c4d56b0..cb6559c 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit c4d56b024c9b8ae5c39572a5ffb3e867eec098db
+Subproject commit cb6559ca7a95f836eb386c04783c9446e7240967