Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Protect vs build-args not consumed

    BRANCH is useless in case of components which only inherits from tempest.
    The build could simply fail depending on the docker version [1].

    [1] https://build.opnfv.org/ci/job/opnfv-functest-components-latest-build/1/console

    Change-Id: I8ced7282c77463de9684904d141b2f18ae45d3c9
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 1d847fa..a246511 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 1d847faa1fe9e874147deec13624367469cb3130
+Subproject commit a246511be00baa78736d7f72954c7884d5e1dd4d