Update git submodules

Update git submodules

* Update docs/submodules/promise from branch 'master'
  - Add promise package

    It eases how Functest installs/runs it (see testcases.yaml [1]).
    The former run_tests.py is renamed to avoid duplicated binaries (see
    [2] and [3]).

    [1] https://git.opnfv.org/functest/tree/functest/ci/testcases.yaml
    [2] https://git.opnfv.org/sdnvpn/tree/sdnvpn/test/functest/run_tests.py
    [3] https://git.opnfv.org/sfc/tree/sfc/tests/functest/run_tests.py

    Change-Id: I626ce6b425399dc5a0a360782352757c26ca1db3
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>