Update git submodules

Update git submodules

* Update docs/submodules/functest from branch 'stable/euphrates'
  - Merge "Prepare Functest euphrates containers" into stable/euphrates
  - Prepare Functest euphrates containers

    They depend on git commit ids for the next OPNFV projects:
      - releng [1]
      - securityscanning

    Securityscanning should be first removed in master and then the patch
    will be cherry-picked in stable/euphrates. A temporarily git commit
    id is used here to allow building the containers before that changes.

    [1] https://lists.opnfv.org/pipermail/opnfv-tech-discuss/2017-September/017865.html

    Change-Id: Ib7bd4206a6ef7f5bb8cd58f324d3e437a3b704a1
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>