Switch from unittest2 compat methods to Python 3.x methods

With the removal of Python 2.x we can remove the unittest2 compat
wrappers and switch to assertCountEqual instead of assertItemsEqual

We have been able to use them since then, because
testtools required unittest2, which still included it. With testtools
removing Python 2.7 support [3][4], we will lose support for
assertItemsEqual, so we should switch to use assertCountEqual.

[1] - https://bugs.python.org/issue17866
[2] - https://hg.python.org/cpython/rev/d9921cb6e3cd
[3] - testing-cabal/testtools#286
[4] - testing-cabal/testtools#277

Change-Id: I7767abc2ed4317288303fc9a2235e869f46a63b0

os_brick/tests/initiator/connectors/test_disco.py

@@ -144,7 +144,7 @@ class DISCOConnectorTestCase(test_connector.ConnectorTestCase):
         """Test to get all the available DISCO volumes."""
         expected = ['/dev/dms1234567']
         actual = self.connector.get_all_available_volumes(None)
-        self.assertItemsEqual(expected, actual)
+        self.assertCountEqual(expected, actual)
 
     def test_extend_volume(self):
         self.assertRaises(NotImplementedError,

os_brick/tests/initiator/connectors/test_fibre_channel.py

@@ -424,7 +424,7 @@ class FibreChannelConnectorTestCase(test_connector.ConnectorTestCase):
         mock_isdir.return_value = False
         expected = []
         actual = self.connector.get_all_available_volumes()
-        self.assertItemsEqual(expected, actual)
+        self.assertCountEqual(expected, actual)
 
     @mock.patch('eventlet.greenthread.sleep', mock.Mock())
     @mock.patch.object(linuxscsi.LinuxSCSI, 'find_multipath_device')

os_brick/tests/initiator/connectors/test_iscsi.py

@@ -919,7 +919,7 @@ Setting up iSCSI targets: unused
         mock_isdir.return_value = False
         expected = []
         actual = self.connector.get_all_available_volumes()
-        self.assertItemsEqual(expected, actual)
+        self.assertCountEqual(expected, actual)
 
     @mock.patch.object(iscsi.ISCSIConnector, '_get_device_path')
     def test_get_potential_paths_mpath(self, get_path_mock):

os_brick/tests/windows/test_fibre_channel.py

@@ -60,7 +60,7 @@ class WindowsFCConnectorTestCase(test_base.WindowsConnectorTestBase):
         else:
             expected_props = {}
 
-        self.assertItemsEqual(expected_props, props)
+        self.assertCountEqual(expected_props, props)
 
     @mock.patch.object(fc.WindowsFCConnector, '_get_scsi_wwn')
     @mock.patch.object(fc.WindowsFCConnector, 'get_volume_paths')