Update git submodules

Update git submodules

* Update docs/submodules/sfc from branch 'master'
  - Adding Dimitris as a committer

    Dimitris has been helping a lot in the 2 previous releases. This last release
    has proven that he is essential to the project adding features like
    multi-installer support and helping debug SFC in both APEX and xci. That's
     why I think he should become committer in the OPNFV-SFC project

    Change-Id: I727e3e4e34b9b8aee24cd2b85af23fe97d601278
    Signed-off-by: Manuel Buil <mbuil@suse.com>