Update git submodules

* Update docs/submodules/releng from branch 'master'
  - xci: Execute prepare-tests.sh to prepare OPNFV VM

    It also fixes the results directory where Functest log is cat from.

    Change-Id: I3d8ea06d3741c70108cdb1c7f040969dbacf79a5
    Signed-off-by: Fatih Degirmenci <fdegir@gmail.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index cad73d7..4f9c2dd 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit cad73d7ba7dffe634c389f9c8eaea9a97ba9b58d
+Subproject commit 4f9c2dd1172ae6f87e607f4bf8c6d63803b1db19