Update git submodules

* Update docs/submodules/yardstick from branch 'stable/fraser'
  - Merge "ping bottlenecks failed when security group rule do not support ipv6 - dovetail" into stable/fraser
  - ping bottlenecks failed when security group rule do not support ipv6 - dovetail

    JIRA: YARDSTICK-1380

    Change-Id: I2163eeb9ab17e4f0216ddaed688e78acdf51a1ff
    Signed-off-by: rexlee8776 <limingjiang@huawei.com>
    (cherry picked from commit 1c5d667f11d9d8a67a262eb6cc5ac53ff9d0cadd)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index a0cae34..297bfc5 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit a0cae34ea1515654309c9d18419ac0caf4c6e5c6
+Subproject commit 297bfc5f20f5b0077968870c2270dcf1b8114724