Update git submodules

Update git submodules

* Update docs/submodules/sfc from branch 'master'
  - Update symmetric chain test case

    Update the symmetric chain test case aligning it with updates available
    from ODL Oxygen:

    - ODL networking-sfc implementation now supports symmetric paths. It is
      no longer needed to configure the ACL or chain directly through the
      ODL rest api. It can now be fully relied on tacker for this.
    - ODL networking-sfc implementation now supports different ingress and
      egress ports for port pairs. The test case exercises this by setting
      up a VNF with two distinct ports. Note that this requires an updated
      VNF image that supports two nics and bundles a vxlan_tool capable of
      using them.

    Change-Id: Ie711abb93109943dcbf699ece7b2b570500a3711
    Signed-off-by: Jaime Caamaño Ruiz <jcaamano@suse.com>