Update git submodules

* Update docs/submodules/yardstick from branch 'stable/danube'
  - cyclictest: use raw strings to escape \[8

    Change-Id: I36d93eacab2470f90af5653104ad5c07853411bf
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>
    (cherry picked from commit 4a16c5c592f48953d0b6678376f540b54135d51c)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index fa463f7..f4f7104 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit fa463f7e2afc9dba9d9af5ac6a5bd7dd2630d17c
+Subproject commit f4f7104e942988e6cf294c3ad80d1a96dc051aaa