Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "Create stable gambia branch for container4nfv"
  - Create stable gambia branch for container4nfv

    Change-Id: Ifb9649f17c951af36a7519cb6d8e07f633280763
    Signed-off-by: Xuan Jia <jason.jiaxuan@gmail.com>
    Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index fdf486f..1a8ff50 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit fdf486fde08a15329db2175a5447d5e3a185a27a
+Subproject commit 1a8ff508b48204ae581c5f20fa8b3ef64c3579a8