Update git submodules

* Update docs/submodules/releng from branch 'master'
  to f8ef2e2114b472456e308d2e0bf977c3b9dcc0db
  - Precise arch when building xtesting containers

    Change-Id: I0fd0e4e2012523e2269dc67e1d0b90c3b9c63c14
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index e8ce5a2..f8ef2e2 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit e8ce5a2409aaca6096bea94ccb40ae2ab5c1351e
+Subproject commit f8ef2e2114b472456e308d2e0bf977c3b9dcc0db