Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Change AutoConnectSSH to return error code by default"
  - Change AutoConnectSSH to return error code by default

    AutoConnectSSH execute method always returns exception when remote
    command returns non 0 ret code. This behavior has been introduced
    by https://gerrit.opnfv.org/gerrit/#/c/58579/ changes which break
    the NSB functionality. There are 200+ places where return code
    (event non zoro) is expected to be returned by
    AutoConnectSSH.execute() method. Right now the method returns
    always exception in case of remote command return not zero which
    causes the problem.

    Changed execute() method to have previous behavior (raise_on_error
    is always False by default) and the exception is raised only in
    case if raise_on_error=True is set explicitly.

    Added UT.

    JIRA: YARDSTICK-1365

    Change-Id: Ib067583ea5eb704b9174084b45b920c24eb307ac
    Signed-off-by: Mytnyk, Volodymyr <volodymyrx.mytnyk@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 81c791a..8d9b872 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 81c791a5598baba57d829f338abde29f7b157b71
+Subproject commit 8d9b8727102545fedaa0e9a144ecb1958f446cd9