@Override
    public HostSpec allocateHost(String alias) {
        return hostSpec;
    }
A host provisioner used when there is no hosts.xml file (using localhost as the only host)
No state in this provisioner, i.e. it does not know anything about the active
application if one exists.

@author hmusum
config-model/src/main/java/com/yahoo/config/model/provision/SingleNodeProvisioner.java