Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "[fuel] Define Docker tag for stable branches"
  - [fuel] Define Docker tag for stable branches

    Change-Id: Ic3c99eee282641eb15880fe18578cbee534308e5
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index e1cda14..70e0b78 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit e1cda14d7990bd7ea65c7952ed756976ce796544
+Subproject commit 70e0b787e9e72a7438be6069ab205c96fc18a53d