Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Delete any previous configuration"
  - Delete any previous configuration

    Delete any previous configuration using the virsh module in ansible:
    Networks, VMs and local IPs.

    JIRA: YARDSTICK-950

    Change-Id: Ie4963ab8210ce50ba2e9fa22642ec27a3b2031e1
    Signed-off-by: John O Loughlin <john.oloughlin@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 7d7f857..c23e4cc 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 7d7f85712ce090dca5439aa60e1dc6418d20f0d2
+Subproject commit c23e4ccf2ed84c44a1d8742b5485c717cf04f452