Update git submodules

* Update docs/submodules/releng from branch 'master'
  to 6c8e1af2e5f78ff2d673175899ed6de56a99d8dd
  - Fix build args logic

    Change-Id: I2eadec7ac35a1cdeca25fad917b8f021ff2c15fa
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index c7bffea..6c8e1af 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit c7bffea1721ac805371d700c68fe14aeb7ce2f03
+Subproject commit 6c8e1af2e5f78ff2d673175899ed6de56a99d8dd