Tests: Fix rbd unit test failure due to ceph keyring file
This test fails if /etc/ceph/ceph.client.admin.keyring
exists.  Mock out isfile() to get the behavior the unit
test expects.
Closes-Bug:
@@ -1657,6 +1657,7 @@ class RBDTestCase(test.TestCase):
# OpenStack usage doesn't have the rbd_keyring_conf Oslo Config option
cfg_file = '/etc/ceph/ceph.client.admin.keyring'
self.driver.configuration.rbd_keyring_conf = cfg_file
+ with mock.patch('os.path.isfile', return_value=False):
self.driver._set_keyring_attributes()
self.assertEqual(cfg_file, self.driver.keyring_file)
self.assertIsNone(self.driver.keyring_data)
