Update git submodules

* Update docs/submodules/releng from branch 'master'
  - leverage tox and pytest to execute unit test

    Change-Id: I20856e1b445587f0d8ee23e792793af863743252
    Signed-off-by: SerenaFeng <feng.xiaowei@zte.com.cn>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index f057556..3f5787e 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit f05755626655aa5532650823f869b513d4b5cd45
+Subproject commit 3f5787e7cd1ee16d549f8dd2d04364d0538afe7f