Update git submodules

* Update docs/submodules/releng from branch 'master'
  to a6a96320d6f8fb1108d3a2f1ec488e71bc4a5bfb
  - Merge "Use sudo when installing disk-image-builder"
  - Use sudo when installing disk-image-builder

    Change-Id: Ifb6783fdb559598ff7fcdbeea12833a32cf15715
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 03eb63a..a6a9632 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 03eb63af4017a92d930d06e0f312656d17be2395
+Subproject commit a6a96320d6f8fb1108d3a2f1ec488e71bc4a5bfb