Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "dovetail: add a suitable job used for vpn test case validation in CI"
  - dovetail: add a suitable job used for vpn test case validation in CI

    JIRA: DOVETAIL-424

    the principle is
    1) not disturb the original work flow
    2) after vpn testcases integrated into dovetail, i.e, CVP tool,
       there is a need to find a POD has bgpvpn feature which is
       suitable to validate bgp vpn test cases in proposed_tests.
    3) only add dovetail proposed_tests into bgpvpn scenario deploy-test loop
       to reduce unnecessary time consuming.
    4) further, should consider to add dovetail job in os-nosdn-nofeature loop

    Change-Id: Iad6ae1e44470c8e9d49a25980d292ba3871bd6a4
    Signed-off-by: MatthewLi <matthew.lijun@huawei.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 9d074ac..937dd2f 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 9d074acbaabef39cade89da70f752e27f760a706
+Subproject commit 937dd2fe36ca5115836a32f78af24adde136e32d