Update git submodules

* Update docs/submodules/releng from branch 'master'
  to e8ce5a2409aaca6096bea94ccb40ae2ab5c1351e
  - Build xtesting-mts

    Change-Id: I4b1c9fa04ccf287152fb166946e78f7cf4797235
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 3bc12ce..e8ce5a2 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 3bc12ce487234b58c0313f24e8ced2db7615ecfd
+Subproject commit e8ce5a2409aaca6096bea94ccb40ae2ab5c1351e