Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Cleanup BaseMonitor unit tests"
  - Cleanup BaseMonitor unit tests

    Stop multiprocessing queues to avoid BrokenPipe exception.
    Assert correctly the raise of exceptions.

    JIRA: YARDSTICK-1229

    Change-Id: I1a1c92c49a439283a35c9a69b59d6866f35ec09a
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index ded9890..f4c002a 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit ded989093f16c2d7d8900b2a3afbc0521d474e08
+Subproject commit f4c002a5b95ad157c88825748f891c7adc1bbe04