Update git submodules

* Update docs/submodules/yardstick from branch 'stable/fraser'
  - Merge "extra loopback cleanup" into stable/fraser
  - extra loopback cleanup

    try to cleanup in the shell script in case ansible errors

    maybe it is hopeless because of docker

    JIRA: YARDSTICK-1096
    JIRA: YARDSTICK-1054

    Change-Id: I759ded4731a7710a194a81530cfb35376eb7800d
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 6af74bd..26083c4 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 6af74bdd4c6b8ae9601e8910273b51c347eed97c
+Subproject commit 26083c4931c0bc72569d782c9df569dc6369077b