Update git submodules

Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Merge "Config test_accounts_file for refstack_defcore"
  - Config test_accounts_file for refstack_defcore

    Tenant and user are required by refstack_defcore, which could
    be configured in the test_accounts_file. [1]

    [1]: https://github.com/openstack/refstack-client/blob/master/refstack_client/refstack_client.py#L170-L193

    Change-Id: I9c920b6f15f491d671ebf222976305bedf4dd747
    Signed-off-by: Linda Wang <wangwulin@huawei.com>