Update git submodules

* Update docs/submodules/releng from branch 'master'
  to 4c1ae6fc5a4655e085d7001cf783c1c01de28431
  - Enable Airship CI

    Functest is ready to verify Airship L2-only scenario.

    This reverts commit 3adc3383bd4395652e86f19e85244ea38cfb24e9.

    Change-Id: I959bd6e65e1d9f4ffe27e26937832470389013aa
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index a19bbaf..4c1ae6f 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit a19bbaf2e8c2046a6747ce97272f017324073a5c
+Subproject commit 4c1ae6fc5a4655e085d7001cf783c1c01de28431