Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Make files pep8 compliant before replacing assertEqual(None, xx)"
  - Make files pep8 compliant before replacing assertEqual(None, xx)

    * tests/unit/network_services/helpers/test_samplevnf_helper.py
    * tests/unit/network_services/traffic_profile/test_rfc2544.py
    * yardstick/tests/unit/common/test_ansible_common.py

    JIRA: YARDSTICK-942
    Signed-off-by: Emma Foley <emma.l.foley@intel.com>
    Change-Id: Ib3c71db5f5774d2bfb3a9cbd260b838eb5501448

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index f28354a..c27266f 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit f28354a8d0c7e3aa190d8c71391d03be4608c70d
+Subproject commit c27266f509dd1fb07d7b03e5c6befe489a95a423