Add migrate_volume to BaseVD

migrate_volume() only exists in the deprecated VolumeDriver()
class and not BaseVD.  This means that drivers inheriting from
*VD hit attribute errors when trying to call driver.migrate_volume().

I suspect this indicates that we should rework some of our
abc class structure a little bit, but this seems like a
reasonable fix for now.

Related-Bug: #1478987
Related-Bug: #1471807
Closes-Bug: #1493286

Change-Id: I3d555507416606db265b8ebe335b51a08fe32328

cinder/tests/unit/test_glusterfs.py

@@ -1792,3 +1792,16 @@ class GlusterFsDriverTestCase(test.TestCase):
             mock_upload_volume.assert_called_once_with(
                 mock.ANY, mock.ANY, mock.ANY, upload_path)
             self.assertEqual(1, mock_create_temporary_file.call_count)
+
+    def test_migrate_volume_is_there(self):
+        """Ensure that driver.migrate_volume() is there."""
+
+        drv = self._driver
+
+        ctxt = context.RequestContext('fake_user', 'fake_project')
+        volume = self._simple_volume()
+        ret = drv.migrate_volume(ctxt,
+                                 volume,
+                                 mock.sentinel.host)
+
+        self.assertEqual((False, None), ret)

cinder/volume/driver.py

@@ -1396,6 +1396,14 @@ class BaseVD(object):
         """
         return None
 
+    def migrate_volume(self, context, volume, host):
+        """Migrate volume stub.
+
+        This is for drivers that don't implement an enhanced version
+        of this operation.
+        """
+        return (False, None)
+
 
 @six.add_metaclass(abc.ABCMeta)
 class LocalVD(object):