Update git submodules

Update git submodules

* Update docs/submodules/samplevnf from branch 'master'
  - Merge "vCGNAPT: correcting to use default rte_ring_dequeue"
  - vCGNAPT: correcting to use default rte_ring_dequeue

    JIRA: SAMPLEVNF-19

    The rte_ring_sc_dequeue returns ENOENT in DPDK16.04 while ENOBUFS in
    DPDK17.05. This leads to error in return value checking and mis behaviour.

    Using of rte_ring_sc_dequeue() to be avoided to use the default
    configuration as set during the creation of the queue as per the
    DPDK API documentation. Similarly corrected for mp_dequeue as well.

    Change-Id: Iacee1349b26d6ab432be891fad12313a6d68ca4d
    Signed-off-by: Anand B Jyoti <anand.b.jyoti@intel.com>