@Override
    public boolean isAsyncComplete(TaskModel task) {
        return true;
    }
Keep Subworkflow task asyncComplete. The Subworkflow task will be executed once
asynchronously to move to IN_PROGRESS state, and will move to termination by Subworkflow's
completeWorkflow logic, there by avoiding periodic polling.

@param task
@return
core/src/main/java/com/netflix/conductor/core/execution/tasks/SubWorkflow.java