Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Updated documentation for stanalone context

    Added details about hosts configurations in order to run tests for
    standalone context.
    Changes made to '13-nsb-installation.rst'.

    JIRA: YARDSTICK-1402

    Change-Id: I4e3304065343014a80b85fc712cdde3ca62d8b2e
    Signed-off-by: Stepan Andrushko <stepanx.andrushko@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 662de49..680de98 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 662de49b9f6c116d15882aed9e678cd3cf67494b
+Subproject commit 680de98b5f0e63fecb795de128448859bd231b6a