Update git submodules

Update git submodules

* Update docs/submodules/samplevnf from branch 'master'
  - Merge "Fix stacking of rx receive functions"
  - Fix stacking of rx receive functions

    PROX can stack different RX functions, so that they are executed
    after each other.
    This feature is for instance used to dump packets or to print
    distribution of receive packets, without influencing the performance
    of the rx functions when no dump or print is needed.
    The previous implementation was wrong and causing some of the stacked
    functions not to be executed. This was causing for instance issues
    in latency measurement after enabling dumping packets.

    Change-Id: I766b8ee8e8852fa17cdaf60ee6e1fec0dc98c719
    Signed-off-by: Xavier Simonart <xavier.simonart@intel.com>