Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Avoid pylint warning for "protected-access"

    This warning should be disabled in order to access protected
    methods during testing. Any access to protected methods done
    outside the testing classes, must be catched during the reviewing
    process.

    Change-Id: I2127b41edf704d0cb4f68b33d98705039e058d1a
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index a55aa99..f11f755 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit a55aa99ae1df1f01abd4f9a9765c136c665772bf
+Subproject commit f11f755048b23a66962304e61691cab7cc639f29