Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Fix Yardstick Docker image ARM build

    Soften sed pattern, in order to cope with new contents of
    ansible/install.yaml, recently modified by change 61173.

    Previous sed pattern does not work anymore against this changed line:
    https://gerrit.opnfv.org/gerrit/#/c/61173/4/ansible/install.yaml@39

    JIRA: YARDSTICK-1411

    Change-Id: I1e1ebd454900252c29263e746470e18e3139e016
    Signed-off-by: Patrice Buriez <patrice.buriez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index e54efd1..e625e16 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit e54efd1af4b07d508327db2cd3aa48e4473e1ba5
+Subproject commit e625e162c2e4f817f1bc6a440d85b3cc59272ac4