Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "run_tests: don't write python bytecode"
  - run_tests: don't write python bytecode

    we usually disable .pyc generate during unittests

    Change-Id: I7d7af7c6d188f5a592d24aa90322edb217ffd8ba
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index c42d562..66ee825 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit c42d56297d22afb4245eae76c43fa762e14993ab
+Subproject commit 66ee8251059315274f98eb1eef4eb3f8dda92b6e