[Trivial]Do not use self in class method

This is to use cls in class method, instead of self.

Change-Id: I8db94bd689c7afe6b9aacd0ca4c5a62ad463e16e
diff --git a/tempest/api/compute/servers/test_server_rescue.py b/tempest/api/compute/servers/test_server_rescue.py
index 17cd443..5a646f9 100644
--- a/tempest/api/compute/servers/test_server_rescue.py
+++ b/tempest/api/compute/servers/test_server_rescue.py
@@ -110,14 +110,14 @@
     create_default_network = True
 
     @classmethod
-    def skip_checks(self):
-        super(BaseServerStableDeviceRescueTest, self).skip_checks()
+    def skip_checks(cls):
+        super(BaseServerStableDeviceRescueTest, cls).skip_checks()
         if not CONF.compute_feature_enabled.rescue:
             msg = "Server rescue not available."
-            raise self.skipException(msg)
+            raise cls.skipException(msg)
         if not CONF.compute_feature_enabled.stable_rescue:
             msg = "Stable rescue not available."
-            raise self.skipException(msg)
+            raise cls.skipException(msg)
 
     def _create_server_and_rescue_image(self, hw_rescue_device=None,
                                         hw_rescue_bus=None,