Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "jjb/releng: fix partial image name matching"
  - jjb/releng: fix partial image name matching

    Docker image building script opnfv-docker.sh tries to remove existing
    images before and after building. It simply uses grep to matching image
    names, which may cause partial name matching problems.
    Ex. opnfv/compass-tasks will match both opnfv/compass-tasks and
    opnfv/compass-tasks-base, and may lead to accidentally removing of
    images still in use when several building tasks run concurrently.

    Error log:
    https://build.opnfv.org/ci/job/compass-tasks-build-arm64-master/6/console

    Change-Id: I1a83f801c5e0cc889cd9e17b8d1b4d895f1f68a9
    Signed-off-by: Yibo Cai <yibo.cai@arm.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 1866b67..c70dfbb 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 1866b67d0f76a8fb4cfc85614be9787683f2b8fe
+Subproject commit c70dfbb4035f18fafbf748216c53906a3b74f2a1