Update git submodules

Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Merge "Fix all rally requirements on-the-fly"
  - Fix all rally requirements on-the-fly

    Rally is released out of OpenStack releases and its requirements must
    be modified before installing. Rally applies a similar solution for
    gating [1].

    [1] https://github.com/openstack/rally/blob/stable/0.9/tests/ci/sync_requirements.py

    Change-Id: I3dfe69597e6ebecc5f07943658634ea94625294f
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>