Update git submodules

Update git submodules

* Update docs/submodules/sfc from branch 'master'
  - Remove custom tacker-client installation script

    In previous releases we used a custom tacker client
    because we also used a custom tacker.

    For the next release we migrate to the the upstream tacker
    so we don't need anymore the aforementioned installation script
    because now we support the upstream tacker client.

    Change-Id: I0c502426161bbeaaf2418823fe91c2025f1494a8
    Signed-off-by: Dimitrios Markou <mardim@intracom-telecom.com>