Update git submodules

* Update docs/submodules/bottlenecks from branch 'stable/fraser'
  - Adjust the doc for stess ping test

    Some changes of stess ping test have been made for Dovetail.
    The patch is to adjust the doc to the new changes.

    Change-Id: I7c6c6fb0f1f60849ec440068fabdf601d76655f1
    Signed-off-by: Yang (Gabriel) Yu <Gabriel.yuyang@huawei.com>
    (cherry picked from commit 5863f141195f79e53c3e70fc62e1593cdc4e6800)

diff --git a/docs/submodules/bottlenecks b/docs/submodules/bottlenecks
index 2dd93f5..8e751cb 160000 (submodule)
--- a/docs/submodules/bottlenecks
+++ b/docs/submodules/bottlenecks
@@ -1 +1 @@
-Subproject commit 2dd93f5cb51e656fad21f50ccbb437aa3f2d1c92
+Subproject commit 8e751cb5c17f2634c0f19aeedc6c4a75e4c3d946