Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Run Functest Gambia verify jobs

    It ensures that the current release is always stable.

    Change-Id: I6a9d479c9c2664493e5685651254c3fca358aec2
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 4818cd9..2b4c8b6 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 4818cd9300b643d2af764639593632f2074e62d3
+Subproject commit 2b4c8b6f9fb1117e44c63804126d2999053a2185