Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "TC042 bug fix"
  - TC042 bug fix

    JIRA:YARDSTICK-786

    yardstick DPDK image have problems to build.
    We will fix this by using nsb image
    the pktgen DPDK testcase will use sampleVNF image

    Change-Id: I24b7b6a9acfe21ec956fa9c4ee7ebe7ae1787dbb
    Signed-off-by: liyin <liyin11@huawei.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 0c64be3..5f5d073 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 0c64be36cd7820c46dd68bffda47fab6fc56ae94
+Subproject commit 5f5d07360188d566b20279e6ebbb1b0acbd8a966