Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "Add slave parameter for zte-pod4"
  - Add slave parameter for zte-pod4

    Change-Id: Icdfc94067313705913ccd215c1f20ca29f7a7e51
    Signed-off-by: Yujun Zhang <zhang.yujunz@zte.com.cn>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 770d1a5..6d415ab 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 770d1a5795e05417092aae6a562ab9fb47b27562
+Subproject commit 6d415ab867543ed2c1fa23e24bcec36581b6fce7