Update git submodules

Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Specify the networks to be used per pod"
  - Specify the networks to be used per pod

    If CRD "Network" is defined and network items are created, each pod (server)
    can have access to one or several networks. This is defined in the metadata
    section, as "annotations.networks" [1].

    Example of Kubernetes pod definition with networks:
      apiVersion: v1
      kind: Pod
      metadata:
        name: test-pod
        annotations:
          networks: '[{"name": "flannel"}]'

    Example of Yardstick server definition with networks:
      context:
        type: Kubernetes
        servers:
          host:
            containers:
              - name: ...
            networks:
              - flannel  # These names must be defined in
                         # context.networks
        ...
        networks:
          - name: flannel
            plugin: flannel

    Kubernetes annotations [2].

    [1]https://github.com/intel/multus-cni/tree/b9446232cdf4f1b6f2bea583291973cc97e963f4#configuring-multus-to-use-kubeconfig-and-a-default-network
    [2]https://kubernetes.io/docs/concepts/overview/working-with-objects/annotations/

    JIRA: YARDSTICK-1178

    Change-Id: I6e7b4bacf10810833ec733c14d44e5db613675e3
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>