"Clocker with Docker Overlay" fails to launch: no sdn.agent.entity

[aledsage]

With clocker 1.2.0-SNAPSHOT (as at commit 7c9346c)

When deploying "Clocker with Docker Overlay" to BlueBox, it fails to start. Each docker host hangs at line SdnAgent agent = Entities.attributeSupplierWhenReady(this, SdnAgent.SDN_AGENT).get();:

Waiting on Task[waiting on sdn.agent.entity]@d08PMBn9

Task[post-start]@vziYsQj5
Submitted by SoftlyPresent[value=Task[start]@vkuJBeus]
Children:
  Task[ssh: check-running DockerHostImpl{id=WYgVkV6G}]@jScWYTIn: Completed, result: 0

In progress, thread waiting (notify) on java.util.concurrent.FutureTask@2844fef0
At: com.google.common.util.concurrent.ForwardingFuture.get(ForwardingFuture.java:63)
    org.apache.brooklyn.util.core.task.BasicTask.get(BasicTask.java:361)
    org.apache.brooklyn.util.time.Durations.get(Durations.java:43)
    org.apache.brooklyn.util.time.Durations.get(Durations.java:64)
    org.apache.brooklyn.util.core.task.ValueResolver$1.call(ValueResolver.java:310)
    org.apache.brooklyn.util.core.task.ValueResolver$1.call(ValueResolver.java:308)
    org.apache.brooklyn.util.core.task.Tasks.withBlockingDetails(Tasks.java:98)
    org.apache.brooklyn.util.core.task.ValueResolver.getMaybeInternal(ValueResolver.java:314)
    org.apache.brooklyn.util.core.task.ValueResolver.getMaybe(ValueResolver.java:257)
    org.apache.brooklyn.util.core.task.ValueResolver.get(ValueResolver.java:250)
    org.apache.brooklyn.util.core.task.Tasks.resolveValue(Tasks.java:139)
    org.apache.brooklyn.core.entity.Entities$6.get(Entities.java:1056)
    clocker.docker.entity.DockerHostImpl.postStart(DockerHostImpl.java:737)
    org.apache.brooklyn.entity.software.base.SoftwareProcessDriverLifecycleEffectorTasks.postStartCustom(SoftwareProcessDriverLifecycleEffectorTasks.java:182)
    org.apache.brooklyn.entity.software.base.lifecycle.MachineLifecycleEffectorTasks$PostStartTask.run(MachineLifecycleEffectorTasks.java:572)
    org.apache.brooklyn.util.core.task.DynamicSequentialTask$DstJob.call(DynamicSequentialTask.java:359)
    org.apache.brooklyn.util.core.task.BasicExecutionManager$SubmissionCallable.call(BasicExecutionManager.java:519)

There are no entities under the Overlay Network's "SDN Host Agents" (and no sensor "sdn.agent.entity" set on the docker host).