Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Improve NSB Standalone XML generation"
  - Improve NSB Standalone XML generation

    Delayed the generation of the XML file until the last step. The
    following functions will return a XML string insted:
    - Libvirt.build_vm_xml
    - SriovContext._enable_interfaces
    - OvsDpdkContext._enable_interfaces

    The XML file will be written just before copying the file to the
    compute hosting the VMs.

    JIRA: YARDSTICK-939

    Change-Id: Icc80f4741903bbe335db4ebccab395b72fa87e82
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index c07a248..052a13a 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit c07a248d10a4cd3c451983a9856eec590e2bfd3d
+Subproject commit 052a13ab65063c2f50468161e278d348a403c660