simplify heat test_limits

the test_limits test has a lot of conventions from other parts
of tempest which are not needed, like the use of setUpClass, and
setting _interface.

To do this we need to assign a client in the base class, further
refactoring should be able to remove a lot of code from these
tests.

This trims this down to the same functional equivalent, but with
less code.

Change-Id: Iabfa9afb7b55c4cdb86c519bce798e548463e7c4
diff --git a/tempest/api/orchestration/base.py b/tempest/api/orchestration/base.py
index 79f8f4a..9bf9568 100644
--- a/tempest/api/orchestration/base.py
+++ b/tempest/api/orchestration/base.py
@@ -36,6 +36,7 @@
 
         cls.os = os
         cls.orchestration_client = os.orchestration_client
+        cls.client = os.orchestration_client
         cls.servers_client = os.servers_client
         cls.keypairs_client = os.keypairs_client
         cls.network_client = os.network_client
@@ -73,13 +74,13 @@
     def clear_stacks(cls):
         for stack_identifier in cls.stacks:
             try:
-                cls.orchestration_client.delete_stack(stack_identifier)
+                cls.client.delete_stack(stack_identifier)
             except exceptions.NotFound:
                 pass
 
         for stack_identifier in cls.stacks:
             try:
-                cls.orchestration_client.wait_for_stack_status(
+                cls.client.wait_for_stack_status(
                     stack_identifier, 'DELETE_COMPLETE')
             except exceptions.NotFound:
                 pass
diff --git a/tempest/api/orchestration/stacks/test_limits.py b/tempest/api/orchestration/stacks/test_limits.py
index 22f544d..893dcc4 100644
--- a/tempest/api/orchestration/stacks/test_limits.py
+++ b/tempest/api/orchestration/stacks/test_limits.py
@@ -24,16 +24,10 @@
 
 
 class TestServerStackLimits(base.BaseOrchestrationTest):
-    _interface = 'json'
-
-    @classmethod
-    def setUpClass(cls):
-        super(TestServerStackLimits, cls).setUpClass()
-        cls.client = cls.orchestration_client
-        cls.stack_name = data_utils.rand_name('heat')
 
     @attr(type='gate')
     def test_exceed_max_template_size_fails(self):
+        stack_name = data_utils.rand_name('heat')
         fill = 'A' * CONF.orchestration.max_template_size
         template = '''
 HeatTemplateFormatVersion: '2012-12-12'
@@ -41,5 +35,5 @@
 Outputs:
   Foo: bar''' % fill
         ex = self.assertRaises(exceptions.BadRequest, self.create_stack,
-                               self.stack_name, template)
+                               stack_name, template)
         self.assertIn('Template exceeds maximum allowed size', str(ex))