Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "Correctly set IMAGE_PROPERTIES in functest-alpine.sh"
  - Correctly set IMAGE_PROPERTIES in functest-alpine.sh

    Change-Id: I4cecaf7302fa1f39aa1e8b2c3e34f11ee49b4359
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index fa61619..6c01646 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit fa61619e64d56bee97df49bc0a80fa6bc7c5da79
+Subproject commit 6c01646f6856db853cac1fd05866ad5d9dda0651