Update git submodules

* Update docs/submodules/yardstick from branch 'stable/fraser'
  - Merge "Replace cinder delete volume with shade client." into stable/fraser
  - Replace cinder delete volume with shade client.

    Function delete volume now uses shade client.

    JIRA: YARDSTICK-891

    Change-Id: I016e1d3bf5972879cad176b56c7282e35413945e
    Signed-off-by: Shobhi Jain <shobhi.jain@intel.com>
    (cherry picked from commit 4c672aa7012a530806a2f8ff2d45a8badb7f7b21)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index dd13dca..61f64de 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit dd13dca9aedeeda181e33f9ca8c56e4a465fa806
+Subproject commit 61f64de8a22c78a5cb81acd60bbc5ed7489b211c