Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "prepare for testresults.opnfv.org's watchdog"
  - prepare for testresults.opnfv.org's watchdog

    Due to the frequent crash in testresults.opnfv.org, watchdog will be introduced
    to monitor the status of docker daemon/testapi container/reporting container,
    to make timely recovery, to make things clear, some refactors included
    in this patch:
    1) leverage container name and image name rather than id
    2) address three conditions during the update
    3) refactor code to be more readable

    Change-Id: Ifa7a6fd94db62d532026b5fad33835b0e2abd9af
    Signed-off-by: SerenaFeng <feng.xiaowei@zte.com.cn>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 7d2d337..4f6caf1 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 7d2d3370744a9f578f9038d658724c631da8c001
+Subproject commit 4f6caf1fc33163e92c77f4f326601860023c4801