Update git submodules

* Update docs/submodules/yardstick from branch 'stable/fraser'
  - Fix "os.path" mock problems during tests

    This patch removes the global mocking applied on "os.path".

    Change-Id: Ia18d2c90195c5408a1852792bdf05b6f0c1ad21f
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>
    Signed-off-by: Emma Foley <emma.l.foley@intel.com>
    (cherry picked from commit d7f8717c3beb1854976e77d56823f482497ffff3)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 18657d0..e88d609 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 18657d0ffc9cbc46a17f1a15cc8e884b1124ebbc
+Subproject commit e88d6092ac3dab2b657247c7f27a2b34d90978dc