Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "'libvirt' guest console in Standalone model"
  - 'libvirt' guest console in Standalone model

    Add support for 'libvirt' guest console in Standalone model.

    Change-Id: I660e641339658d8abe4f040bec96e9d0041402c6
    Signed-off-by: Jan Malanik <janx.malanik@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index ccc7cf9..810f91e 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit ccc7cf93bd769f2b9255ac59e93751535b463f2a
+Subproject commit 810f91e242a5d1a562712df72a9ec95605ed1bab