Fix availability zone client in compute admin test

In /tempest/api/compute/admin/test_availability_zone.py file,
V3 test class use the V2 Availability Zone client.

This patch correct the client for V2 and V3 by instantiating the
correct one in base class.

Change-Id: I97903b1ea7faa02c5880c091a166e386295de0da
diff --git a/tempest/api/compute/admin/test_availability_zone.py b/tempest/api/compute/admin/test_availability_zone.py
index 9555367..3a6de36 100644
--- a/tempest/api/compute/admin/test_availability_zone.py
+++ b/tempest/api/compute/admin/test_availability_zone.py
@@ -26,7 +26,7 @@
     @classmethod
     def setUpClass(cls):
         super(AZAdminV3Test, cls).setUpClass()
-        cls.client = cls.os_adm.availability_zone_client
+        cls.client = cls.availability_zone_admin_client
 
     @test.attr(type='gate')
     def test_get_availability_zone_list(self):
diff --git a/tempest/api/compute/base.py b/tempest/api/compute/base.py
index 7c70aec..fdbe123 100644
--- a/tempest/api/compute/base.py
+++ b/tempest/api/compute/base.py
@@ -390,8 +390,11 @@
                 msg = ("Missing Compute Admin API credentials "
                        "in configuration.")
                 raise cls.skipException(msg)
+        if cls._api_version == 2:
+            cls.availability_zone_admin_client = (
+                cls.os_adm.availability_zone_client)
 
-        if cls._api_version == 3:
+        else:
             cls.servers_admin_client = cls.os_adm.servers_v3_client
             cls.services_admin_client = cls.os_adm.services_v3_client
             cls.availability_zone_admin_client = \