nova boot instance can not assign availability zone

[ferry]

 I using the NovaServers.boot_server_from_volume_and_delete yaml and assign the availability_zone ,but it still using the default availability zone no

novaclient.exceptions.BadRequest: The requested availability zone is not available (HTTP 400) (Request-ID: req-12702ccb-8808-4331-9c29-9d909839ca37)
---
  NovaServers.boot_server_from_volume_and_delete:
    -
      args:
        flavor:
            name: "m1.medium"
        image:
            name: "cirros-0.5.1"
        volume_size: 50
        volume_type: "yyyyyyy"
        availability_zone:
          name: "xxxxxxxx"
        auto_assign_nic: true
        nics:
          - net-id: "32cc232a-5ed0-47d1-8181-28bbbbc4d22b"
      runner:
        type: "constant"
        times: 1
        concurrency: 1
      context:
        users:
          tenants: 1
          users_per_tenant: 1
      sla:
        failure_rate:
          max: 0