Update git submodules

Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Merge "Allow building containers from a gerrit change"
  - Allow building containers from a gerrit change

    It leverages on git command instead of pip git support [1].
    Otherwise it forces pip master which raises side effects in rally [2]

    It is mandatory for implementing Functional testing gating [3]

    [1] https://pip.pypa.io/en/stable/reference/pip_install/#git
    [2] https://gerrit.opnfv.org/gerrit/#/c/40909/
    [3] https://wiki.opnfv.org/display/functest/Functional+testing+gating

    Change-Id: Ia18fee3e60fc08da9b96730ce85d5b7c866144aa
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>