Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - nsb_setup: pin pip versions for ansible, shade, docker

    Change-Id: Ia1f1c26becdc776ce664b4ab2fb0254049087318
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 15d9333..734acb2 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 15d9333cf16c533cd438ca4195f50e91b479feec
+Subproject commit 734acb27083ce324b95eedc3643ba1b1d81a1816