Remove Nova v3 API tests

Nova v3 API has disappeared, and Tempest isn't testing the API on the
gate now. In addition, Nova team is creating a new REST API "Nova v2.1
API + microversions" and the interfaces are different from v3 API.
So it is not necessary to keep Nova v3 API tests in Tempest.
This patch removes them.

Change-Id: I5de01deaa699e03b0e838952239011da54702daf
diff --git a/tempest/api/compute/servers/test_availability_zone.py b/tempest/api/compute/servers/test_availability_zone.py
index 28eb274..5ddf053 100644
--- a/tempest/api/compute/servers/test_availability_zone.py
+++ b/tempest/api/compute/servers/test_availability_zone.py
@@ -17,15 +17,15 @@
 from tempest import test
 
 
-class AZV3Test(base.BaseComputeTest):
+class AZV2TestJSON(base.BaseComputeTest):
     """
     Tests Availability Zone API List
     """
-    _api_version = 3
+    _api_version = 2
 
     @classmethod
     def resource_setup(cls):
-        super(AZV3Test, cls).resource_setup()
+        super(AZV2TestJSON, cls).resource_setup()
         cls.client = cls.availability_zone_client
 
     @test.attr(type='gate')
@@ -34,7 +34,3 @@
         resp, availability_zone = self.client.get_availability_zone_list()
         self.assertEqual(200, resp.status)
         self.assertTrue(len(availability_zone) > 0)
-
-
-class AZV2TestJSON(AZV3Test):
-    _api_version = 2