Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Fix Python3 Errors for Release Automation

    My testing was done using Python 2.7 but the build server running the
    jobs is obviously running Python3.

    These changes allow the create_branch.py release script to run against
    both Python2 and Python3.

    Change-Id: I02478986ef869ce82ece5b96dbb4b5ed548a2a55
    Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 34687c0..6f70831 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 34687c0bcbe0d23b0734d75936468aa83b2a71d7
+Subproject commit 6f708314978187243424be89f4f6c0a1d14cb338