Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "bugfix: /resources.json and /APIs cannot be accessed"
  - bugfix: /resources.json and /APIs cannot be accessed

    1. change the join way of discover_url
    2. limit tornado version not to use latest 4.5

    Change-Id: I39dfd3b32bf232a7c144087bc9d5f88fb6798ee7
    Signed-off-by: SerenaFeng <feng.xiaowei@zte.com.cn>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index be35124..f141579 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit be3512443d1e386fb7d65b8a932a54190bd08da5
+Subproject commit f1415796efec4984962f9817639a5ff2cd9ecd41