Code to pass through transport_key_id when storing secret

This can happen in either a PUT or a GET request.  The
SecretStorePluginManager must return the plugin corresponding to
the transport_key_id, and must pass the transport_key as part
of the SecretDTO, so that the plugin will know the contents are
encrypted.

Implements: blueprint add-wrapping-key-to-barbican-server
Change-Id: Ieaa2bb7881cd34bcd891764945ef3c159062d4d4

barbican/tests/plugin/interface/test_secret_store.py

@@ -137,7 +137,7 @@ class WhenTestingSecretStorePluginManager(testtools.TestCase):
         self.assertRaises(
             str.SecretStoreSupportedPluginNotFound,
             self.manager.get_plugin_store,
-            True,
+            transport_key_needed=True,
         )
 
     def test_get_store_with_tkey(self):
@@ -146,5 +146,6 @@ class WhenTestingSecretStorePluginManager(testtools.TestCase):
         plugin2 = TestSecretStoreWithTransportKey(False)
         plugin2_mock = mock.MagicMock(obj=plugin2)
         self.manager.extensions = [plugin1_mock, plugin2_mock]
-        self.assertEqual(plugin2,
-                         self.manager.get_plugin_store(True))
+        self.assertEqual(
+            plugin2,
+            self.manager.get_plugin_store(transport_key_needed=True))