Update git submodules

Update git submodules

* Update docs/submodules/samplevnf from branch 'master'
  - Merge "Fix checks done when changing generator pkt_size"
  - Fix checks done when changing generator pkt_size

    Different checks were done when setting the generator pkt_size.
    In case of wrong pkt_size (e.g. too big) an error was printed but
    the pkt_size was still set causing a potential corruption.
    In addition, in case of a packet size incompatible with some
    of the packet fields (e.g. latency data) PROX was panicing
    while this should not happen runtime for such an error.

    Change-Id: Ifa11475bf295aaac7b0255c1bf9b5feed8ef90c4
    Signed-off-by: Xavier Simonart <xavier.simonart@intel.com>