Update git submodules

* Update docs/submodules/yardstick from branch 'stable/fraser'
  - Merge "Replace nova attach volume to server with shade client." into stable/fraser
  - Replace nova attach volume to server with shade client.

    Function attach_volume_to_server now uses shade client
    instead of nova client.

    JIRA: YARDSTICK-1088

    Change-Id: Id00df672c2c195b5c338cbbc30ddf2742a4e4d29
    Signed-off-by: Shobhi Jain <shobhi.jain@intel.com>
    (cherry picked from commit 8fd82cd8d0146d8cebbc32ed7cbb6fb9d1861297)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 175872b..e8a0b1b 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 175872bec1692c26a321892b356bc5b46b1559d5
+Subproject commit e8a0b1b9662e323499de66aaf3800750f51c1299