Update git submodules

Update git submodules

* Update docs/submodules/functest from branch 'stable/euphrates'
  - Add BRANCH as Docker build arg

    It conforms with the prerequisite of the current releng Docker script.
    BRANCH can be considered as useless because releng already clones the
    right git branch.

    It's a temporarily solution before modifying a script used by lots of
    OPNFV projects.

    Conflicts:
        docker/components/Dockerfile
        docker/healthcheck/Dockerfile

    Change-Id: I585d7a79a9ebaeaffd69af1da1731c44e131f6b5
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>
    (cherry picked from commit 9e72ad1edd88aada55a0328cd72d4941c4e6fc60)