Tests: Mock sleep in cinder test_attachment_create_retries

This brings the time to run this unit test
from 6+ seconds to 0.003s.

Change-Id: I0c40e33bb7f35555b50ca04f1b048d9b716b77b5

glance_store/tests/unit/common/test_cinder_utils.py

@@ -74,6 +74,7 @@ class CinderUtilsTestCase(base.BaseTestCase):
             self.volume_api.attachment_create,
             self.fake_client, self.fake_vol_id)
 
+    @mock.patch('time.sleep', new=mock.Mock())
     def test_attachment_create_retries(self):
 
         fake_attach_id = 'fake-attach-id'