replace 'data=' with 'message='

Replace keyword 'data=' with 'message='

Change-Id: Ic4b0ba3136f27722511cc49bca21568f7b518618

manila/tests/test_utils.py

@@ -593,7 +593,7 @@ class TestRetryDecorator(test.TestCase):
             def fails_once():
                 self.counter += 1
                 if self.counter < 2:
-                    raise exception.ManilaException(data='fake')
+                    raise exception.ManilaException(message='fake')
                 else:
                     return 'success'