Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Add MQ consumer, producer and payload base classes

    Added MessagingProducer base class. A class implementing this base class
    can send a cast message using the MQ service installed in the Yardstick
    jumphost (RabbitMQ by default, other MQ could be implemented). The producer
    will send messages to an specific topic.

    Added MessagingConsumer base class. A class implementing this base class
    will be able to receive any message sent by a MessagingPorducer class
    publishing messages in the topic subscribed.

    By default both Producer and Consumer "fanout" is True. That means every
    Consumer will create a fanout Queue attached to the MQ Exchange topic. All
    Consumers attached to this topic will receive the message sent by the
    Producer [1].

    Added Payload base class. To send data through the message queue service,
    a Payload derived object should be created. This base class allows to
    define the attributes container in the class, convert the object to a dict
    and retrieve the object from a dict.

    Added a new library, "oslo.messaging", to implement the RPC client and
    server.

    [1]http://blog.thedigitalcatonline.com/blog/2013/08/21/some-tips-about-amqp-direct-exchanges/

    JIRA: YARDSTICK-1074

    Change-Id: I63932b5fb3de2bdc1270fc83295630a2a349e2a6
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>