Update git submodules

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

    Function delete_keypair now uses shade client.

    JIRA: YARDSTICK-1088

    Change-Id: I46b895748c5c44b0bf7d5b035395676ebff48d7f
    Signed-off-by: Shobhi Jain <shobhi.jain@intel.com>
    (cherry pick from commit aded0fdb30caf035e0eb94c1216f436ba597c2c7)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 0aade5b..175872b 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 0aade5b529d2115513d5984b66dd37c347e086d3
+Subproject commit 175872bec1692c26a321892b356bc5b46b1559d5