Policies derived from tosca.policies.Placement are not translated

Some policies derived from standard policies are translated by base policy translator.
For example, a policy which has `tosca.policies.tacker.Alarming` type derived from `tosca.policies.Monitoring` type is translated by a translator for `tosca.policies.Monitoring` type.

But a policy which has a type derived from tosca.policies.Placement doesn't seems to be translated by a translator for `tosca.policies.Placement`.

I defined the policy like below

::

  tosca.policies.tacker.Placement:
    derived_from: tosca.policies.Placement
    description: Defines policy for placement the given targets.

and I tried to translate a template like next YAML

.. code::yaml

  topology_template:
    node_templates:
      VDU_Primary:
        type: tosca.nodes.nfv.VDU.Tacker
      VDU_Secondary:
        type: tosca.nodes.nfv.VDU.Tacker
    policies:
      - my_compute_placement_policy:
          type: tosca.policies.tacker.Placement
          description: Apply my placement policy to my application servers
          targets: [ VDU_Primary, VDU_Secondary ]
          properties:
            policy: anti-affinity
            mandatory: false

then I got next error.

::

  heat-translator failed: - Type "tosca.policies.tacker.Placement" is valid TOSCA type but translation support is not yet available.