Update git submodules

* Update docs/submodules/releng from branch 'master'
  to f877ce23a63fc1c9bb3db96adcf9ec4bd58baead
  - Select user opnfv instead of ubuntu

    CNTT and Airship jumphosts differ about the user.

    Change-Id: I129ce7406de4819804f0143fe5ae37d7107064f8
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index fb80065..f877ce2 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit fb8006581900910bb77eae9fa0a852b853a30a4a
+Subproject commit f877ce23a63fc1c9bb3db96adcf9ec4bd58baead