Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - NSB: Fix standalone.model.Libvirt SR-IOV modeling

    Fixed standalone.model.Libvirt SR-IOV XML interface modeling, acording
    to [1]:
    - All PCI attributes now are printed in hexadecimal format.
    - The PCI address is now added in the correct section, 'interface'.

    network_services.utils.PciAddress was refactored to accept both 'domain:
    bus:slot:function' and 'bus:slot:function' format inputs. This class is
    used as input in the previous class, Libvirt, to print in XML the PCI
    address of a SR-IOV interface.

    network_services.utils.PciAddress.parse_address is now deprecated. Instead
    the class standard instantiation must be used:

        libvirt_obj = utils.PciAddress(text_with_address)

    A deprecation decorator is implemented along with this patch. This
    decorator is used for the first time in the previously mentioned function.
    This decorator stores every decorated function name and deprecation message
    and raises a logging warning message the first time this function is used.

    [1] https://goo.gl/so2Mrp

    Change-Id: I22e95c488e27d6e2a8fdf6c1a07faab275fa6bba
    Signed-off-by: Dino Simeon Madarang <dinox.madarang@intel.com>
    Reviewed-by: Alain Jebara <alain.jebara@intel.com>
    Reviewed-by: Deepak S <deepak.s@linux.intel.com>
    Reviewed-by: Ross Brattain <ross.b.brattain@intel.com>
    Reviewed-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 93f53ca..6cfec77 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 93f53ca898891f5fd5fb5994c40932900aea1e73
+Subproject commit 6cfec77db6b95af5b31b741d513955ee3dfa3bb2