Update git submodules

Update git submodules

* Update docs/submodules/samplevnf from branch 'master'
  - Merge "Fix potential crash if link speed is null"
  - Fix potential crash if link speed is null

    Link_speed could be null when prox started with the ports down.
    This was potentially causing a crash.
    Another task will need to update link speed when the port come
    up. Failing to do this results in less accurate latencies
    (no extrapolation)

    Change-Id: I597b68e30117e6edb9ccb4732c2acedd5eb8ac80
    Signed-off-by: Xavier Simonart <xavier.simonart@intel.com>