Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Define several containers per pod in a replication controller"
  - Define several containers per pod in a replication controller

    Add the ability to define not only one but many containers per pod in a
    replication controller descriptor. This feature must be backwards
    compatible; all current test cases using the "single container" server
    definition must be accepted.

    Example of single container pod definition:

      context:
        type: Kubernetes
        servers:
          host:
            image: ...
            commands: ...
            volumes:
              - name: volume1              # mandatory
                <volume type definition>   # mandatory

    Example of several container pod definition:

      context:
        type: Kubernetes
        servers:
          host:
            containers:  # if this key is present, all container specific
                           parameters (image, commands, args, volumeMounts, etc.)
                           must be defined per container
              - image: ...
                commands: ...
              - image: ...
                commands: ...
            volumes:
              - name: volume1              # mandatory
                <volume type definition>   # mandatory

    NOTE: other parameters, like "volumes" or "nodeSelector", are common to all
    containers in the pod.

    JIRA: YARDSTICK-1155

    Change-Id: Ib95668c68e9c09e6de3f1aa41c903cc52e6809ad
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>