Update git submodules

* Update docs/submodules/releng from branch 'master'
  to 9a9f20d715f5a890775748d6b8506369f2ce9fd7
  - Temporarily disable sig_network_serial

    Change-Id: I5f006172c9b8e7aace5ffed01e255fd11c0b98a7
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index bd025ba..9a9f20d 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit bd025ba74346e48357a8ffbd5237b34bd0c0dc7f
+Subproject commit 9a9f20d715f5a890775748d6b8506369f2ce9fd7