Update git submodules

* Update docs/submodules/releng from branch 'master'
  to b2d1bf8e0916902cbd17f5e8c8fd8768126367bc
  - Run opnfv/functest-kubernetes-smoke sequentially

    Now multithreading is enabled at test case level.

    Change-Id: Ia5cfaccfe357ba0f831083bc436007e5d02269ea
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index c53f8a7..b2d1bf8 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit c53f8a7efd1e714c9a9fed1a7c3660403024ec22
+Subproject commit b2d1bf8e0916902cbd17f5e8c8fd8768126367bc