Update git submodules

Update git submodules

* Update docs/submodules/samplevnf from branch 'master'
  - Improve l3fwd performance

    JIRA: SAMPLEVNF-128

    Improve performance of l3fwd use-case.
    L3fwd did not disable TX offload flags, which resulted in
    non-vector mode to be used in pmd in some cases like bare-metal.
    Note that in some cases such as virtio, vector mode was already
    used as OVS reports that it does not support TX-offload, hence
    TX-offload was already disabled on virtio.
    Using vector mode usually brings higher performance.

    Change-Id: I102b846d604a9cf28c6b7dae8bedbe918ccfcf6c
    Signed-off-by: Xavier Simonart <xavier.simonart@intel.com>