Fix Stack instance delete method

The current instance delete method assumes that a Stack
instance can be passed to the manager delete method, however
the manager delete method only accepts a stack identifier.

Change-Id: I87c30be1ea43695b7e13953531ea282fd8d386f8

heatclient/tests/test_stacks.py

@@ -15,6 +15,7 @@
 
 from heatclient.v1.stacks import Stack
 
+from mock import MagicMock
 import testscenarios
 from testscenarios.scenarios import multiply_scenarios
 import testtools
@@ -43,3 +44,12 @@ class StackStatusActionTest(testtools.TestCase):
         stack = Stack(None, {'stack_status': stack_status})
         self.assertEqual(self.action, stack.action)
         self.assertEqual(self.status, stack.status)
+
+
+class StackOperationsTest(testtools.TestCase):
+
+    def test_delete_stack(self):
+        manager = MagicMock()
+        stack = Stack(manager, {'id': 'abcd1234'})
+        stack.delete()
+        manager.delete.assert_called_once_with('abcd1234')

heatclient/v1/stacks.py

@@ -28,7 +28,7 @@ class Stack(base.Resource):
         self.manager.update(self, **fields)
 
     def delete(self):
-        return self.manager.delete(self)
+        return self.manager.delete(self.id)
 
     def data(self, **kwargs):
         return self.manager.data(self, **kwargs)