Update git submodules

* Update docs/submodules/yardstick from branch 'stable/fraser'
  - Move tests: unit/network_services/{lib/,collector/,*.py}

    * Fix pylint errors
    * Add TODOs

    Some errors are ignored locally, as they were a symptom of other problems.
    These issues have been flagged with a TODO, and should be fixed later.

    JIRA: YARDSTICK-837
    Signed-off-by: Emma Foley <emma.l.foley@intel.com>
    Change-Id: Idc2e70291b6d9b4cf7e7249a10c4a290b999206c
    (cherry picked from commit 2e75e6d27240945ec985998bbe9ec6241d11626a)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 7411096..c87a543 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 7411096e94f7e30f03c73cc0b8d66dbd076fc37e
+Subproject commit c87a5438961cba359629800b31df3ad7f656aff8