Update git submodules

Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "[Functest] Adapt set-functest-env to download OS images"
  - [Functest] Adapt set-functest-env to download OS images

    When [1] is ready and merged, we don't need to download the
    OS images that are not needed for the deployed scenario.
    The same filter applies to armband jobs.

    [1] https://gerrit.opnfv.org/gerrit/#/c/37373/

    Change-Id: I5813c738a8d9fa1262299cc50993557757f6d7e8
    Signed-off-by: jose.lausuch <jose.lausuch@ericsson.com>