Update git submodules

Update git submodules

* Update docs/submodules/sfc from branch 'master'
  - Merge "Switch from CONST to env.get()"
  - Switch from CONST to env.get()

    env.get() ensures that default values are reused if unset.
    It also avoids desynchronization between os.environ and CONST.

    It follows the change "Get properly env vars or their default values"
    [1] applied in Functest.

    It also fixes minor issues on shebangs and takes several pylint rules
    into account in this module:
      - http://pylint-messages.wikidot.com/messages:w0702
      - https://www.python.org/dev/peps/pep-0282/

    [1] https://gerrit.opnfv.org/gerrit/#/c/52221/

    Change-Id: Ia7ad168b2cbbade8ea3890fb95dc01bcdfc50468
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>