Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Change assert statements to raises in CheckValue"
  - Change assert statements to raises in CheckValue

    * Instead of using assert statements, raise a custom exception.
    * Modify the unit tests so that they do not test unused parameters for
      equality.
    * Fix pylint and pep8 errors.

    JIRA: YARDSTICK-966

    Change-Id: I41e13a5a22086827792eaf9de8da2e4ed6dd42de
    Signed-off-by: Miikka Koistinen <miikka.koistinen@nokia.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 60e3264..c4e5cb9 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 60e326463ae06038facf79f14e29901e9596e0dc
+Subproject commit c4e5cb946f068c59ebf29274cdf4c9f860a0b07a