Update git submodules

* Update docs/submodules/releng from branch 'master'
  to ccb9b80a4d16cc3948eef74d393b57b7e2a2200d
  - Avoid prompt properly when calling docker system prune

    Change-Id: I472f67b9eebc138f60e50bb70b084db7878e304f
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 0141ae9..ccb9b80 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 0141ae9141d5678fe2cd99906e953c5a80afecc6
+Subproject commit ccb9b80a4d16cc3948eef74d393b57b7e2a2200d