Update git submodules

Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "Add a dovetail test job on huawei-pod4 to test Apex danube branch"
  - Add a dovetail test job on huawei-pod4 to test Apex danube branch

    1. Apex doesn't have danube jobs now.
    2. Dovetail is based on opnfv danube branch, so it should be tested
       against Apex danube deployment.
    3. Huawei-pod4 deployed with Apex danube (os-nosdn-nofeature-ha) and
       can be used to test.

    JIRA: DOVETAIL-494

    Change-Id: Ic3251585503c15fb416c6d9497e8acfc977ebe3e
    Signed-off-by: xudan <xudan16@huawei.com>