Add __ne__ built-in function

In Python 3 __ne__ by default delegates to __eq__ and inverts the
result, but in Python 2 they urge you to define __ne__ when you
define __eq__ for it to work properly [1].
[1]https://docs.python.org/2/reference/datamodel.html#object.__ne__

Change-Id: Ibc8ca97679c1e036290d8e745eae2dbbca4913ad

rally/plugins/openstack/scenarios/vm/utils.py

@@ -86,6 +86,9 @@ class Host(object):
                 other, Host.__class__.__name__))
         return self.ip == other.ip and self.status == other.status
 
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
 
 class VMScenario(nova_utils.NovaScenario, cinder_utils.CinderScenario):
     """Base class for VM scenarios with basic atomic actions.

tests/unit/test_mock.py

@@ -36,6 +36,9 @@ class Variants(object):
     def __eq__(self, val):
         return getattr(val, "variants", val) == self.variants
 
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
     def __contains__(self, val):
         return val in self.variants