Update git submodules

* Update docs/submodules/releng from branch 'master'
  - [Functest] Remove former way to execute prepare_env

    It was used in Danube and there are no more Functest jobs
    that are runnign stable/danube branch.

    Change-Id: I8e8b1f769b76ad511af6086b7a21dd9ae94404f0
    Signed-off-by: Jose Lausuch <jalausuch@suse.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 924e1f3..672dcd6 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 924e1f3fbde9aea8f7c371ebf52d91103930b968
+Subproject commit 672dcd6af0de50c026abab58f0483092461b1719