Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Create a SampleVNF MQ consumer class

    This new class is designed to be used in a ``GenericVNF`` object (VNF
    or traffic generator) in a builder pattern. This consumer class will
    be instantiated when initializing the ``GenericVNF`` derived object.
    The ``GenericVNFConsumer`` endpoint is the ``GenericVNF``derived object
    itself.

    ``GenericVNFEndpoint`` is an interface class to be inherited in a
    ``GenericVNF`` child object; the VNF object will implement the endpoints
    methods.

      NewVNF(GenericVNF, GenericVNFEndpoint):
        def __init__(self, name, vnfd, task_id):
          ...
          self._consumer = vnf_base.GenericVNFConsumer([task_id], self)
          self._consumer.start_rpc_server()

    JIRA: YARDSTICK-1293

    Change-Id: I1bcd980352099e9ebefdab0c96d51aa46f6a1e54
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>