Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "Avoid jenkins substitutions"
  - Avoid jenkins substitutions

    It's currently failing as DOCKER_TAG is replaced by '' [1].

    [1] https://build.opnfv.org/ci/job/functest-apex-baremetal-daily-gambia/21/console

    Change-Id: I3737c683fd85f6c426fdf2720b016f3452eab0b6
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 30f8b6e..d2b0f38 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 30f8b6e0d90b8c4fcc8a169757d10db4b935bad2
+Subproject commit d2b0f38a91aecd4259a3b060553d1429ec5babe3