test_find_resource fails if run alone

Currently, we set 'NAME_ATTR' attribute for Volume and Snapshot
class in volume.client.py. When we test test_find_resource alone,
the Volume and Snapshot class do not have 'NAME_ATTR' attribute since
we do not import volume.client, which causes the tests to fail.

Change-Id: I06f727ffa8d37afe1a1191c36574887fecc7a733
Closes-Bug: #1353788
Merge "test_find_resource fails if run alone"