Update git submodules

* Update docs/submodules/releng from branch 'master'
  to 81f941ffe09697d05e904e5f13f45e8cceb89057
  - Clean former branches

    Change-Id: I206b708fccd27c2c1201bd18e3f62d5d22baf83d
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index fcde3b3..81f941f 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit fcde3b3082c143ec061d28d5166c27c9cc1b183e
+Subproject commit 81f941ffe09697d05e904e5f13f45e8cceb89057