Update git submodules

* Update docs/submodules/releng from branch 'master'
  to bff28787740d77257ae44cc7f208b29297a69d8e
  - nit: fix shell script

    Change-Id: I7c64bfdb0afd906f9df237e8215262e091ac5a22
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index d573696..bff2878 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit d573696d9d5e3b1c617cb38377cb8975c113d683
+Subproject commit bff28787740d77257ae44cc7f208b29297a69d8e