Update git submodules

Update git submodules

* Update docs/submodules/samplevnf from branch 'master'
  - Increase default mbuf size and code simplification/cleanup

    mbuf size was setup to achieve the best performance i.e.
    using the smallest mbuf and not segmenting packets.
    However this resulted in complex code, much dependent of the way
    the pmd are working e.g. a change(fix) in recent dpdk i40e
    implementation caused a 1782 (=1518+8+256) bytes mbuf to be too
    small to hold a 1518 bytes packets.
    Hence this change simplifies the mbuf size selection at the price
    of a potential decreases in performance - as more memory is now used.
    Except if jumbo frames are used, the mbuf size will now be the same
    for all modes. The packets will not be segmented except if jumbo
    frames are enabled.
    If jumbo frames are enabled, packets are by default segmented, except
    if the mbuf size is configured big enough in the config file.

    Change-Id: I222fcac7a65c0d221d5d422f419deb9c0f864172
    Signed-off-by: Xavier Simonart <xavier.simonart@intel.com>
    Signed-off-by: Deepak S <deepak.s@linux.intel.com>