Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Refactor benchmark.core.test_plugin.PluginTestCase"
  - Refactor benchmark.core.test_plugin.PluginTestCase

    Tests in benchmark.core.test_plugin.PluginTestCase are not covering
    correctly the functionality of the tested class.

    YARDSTICK-851

    Change-Id: I0b4cda7dbf109776a202167abfde8c9eb268db12
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index a0e7bc3..0b9b983 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit a0e7bc354558278d3f566e8abe9886e18050e887
+Subproject commit 0b9b983429994eadacedd4cdf51d63e02da31f46