Mock time.sleep in ISCSIConnectorTestCase

When '_test_connect_volume' is run, 'wait_for_volume_removal'
will be called. Neither this method, nor time.sleep is mocked, for
which reason this test will take about 20 seconds to complete.

This patch simply mocks time.sleep for this test.

Change-Id: Iceb0d30ce9f831f5929387eca6918500bbdab944

os_brick/tests/initiator/test_connector.py

@@ -434,6 +434,7 @@ class ISCSIConnectorTestCase(ConnectorTestCase):
                            'multipath_id': FAKE_SCSI_WWN}
         self.assertEqual(expected_result, result)
 
+    @mock.patch('time.sleep', mock.Mock())
     def _test_connect_volume(self, extra_props, additional_commands,
                              transport=None, disconnect_mock=None):
         # for making sure the /dev/disk/by-path is gone