Update git submodules

Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Merge "API proposal for functest"
  - API proposal for functest

    1. Propose a basic framework for API
    2. And these functions have been realized:
       1) Show environment
       2) Prepare Environment
       3) Show credentials
       4) List all testcases
       5) Show a testcase
       6) List all tiers
       7) Show a tier
       8) List all testcases within given tier

    JIRA: FUNCTEST-843

    Change-Id: Ib961446708077b56465eda0052f6d38806b62594
    Signed-off-by: Linda Wang <wangwulin@huawei.com>