Update git submodules

* Update docs/submodules/releng from branch 'master'
  to da6ff45d318e4bb3a9182f0fd931e667421f2250
  - Install software-properties-common gpg

    Change-Id: I9988b328be6ccd5660f2028fafdcc07c0b1c3e78
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 51a1b79..da6ff45 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 51a1b794c8abfb4468ee23cefa54b7474c359aea
+Subproject commit da6ff45d318e4bb3a9182f0fd931e667421f2250