Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Generate pod.yaml from current context"
  - Generate pod.yaml from current context

    We want to generate pod.yaml from Heat contexts so we can
    re-use the context without destroying it.

    But we don't have node role information and it doesn't
    make sense in this case, so make the role optional.

    Since we changed Heat to use pkey instead of key_filename,
    we can embed the pkey into the pod.yaml, but we have
    to make sure to convert the pkey to string, in case
    it is a RSAKey object

    Change-Id: Ibefcfbd8236e68013a704c39964cb870da825da8
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 62c775f..d374dc8 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 62c775f7261dca0081283fadcaa18e53cf2f181c
+Subproject commit d374dc8ca09e7d6e08a531e68a21a8b107af21d0