Fix guardmap as a function object issue in service_guard()

The issue was the original commit had a bug (using the wrong variable),
and also that there were no tests to verify the functionality.  This
patchset fixes the bug and adds tests to verify the contract.

Change-Id: Ia8b5580132c5a592461a57fb514994ab64a9ed42
Closes-Bug: #1805128

hooks/nova_cc_utils.py

@@ -1256,7 +1256,7 @@ def service_guard(guard_map, contexts, active=False):
                         _contexts = contexts
                 incomplete_services = []
                 for svc in _guard_map:
-                    for interface in guard_map[svc]:
+                    for interface in _guard_map[svc]:
                         if interface not in _contexts.complete_contexts():
                             incomplete_services.append(svc)
                 ret = f(*args, **kwargs)

unit_tests/test_nova_cc_utils.py

@@ -1062,6 +1062,69 @@ class NovaCCUtilsTests(CharmTestCase):
         self.assertFalse(self.service_stop.called)
         self.assertTrue(_mc.called)
 
+    def test_service_guard_active_with_guardmap_function_object(self):
+        class MockContext(object):
+            called = False
+
+            def complete_contexts(self):
+                self.called = True
+                return ['interfacea', 'interfaceb']
+
+        _mc = MockContext()
+
+        def guard_map():
+            return {'test': ['interfacea', 'interfaceb']}
+
+        @utils.service_guard(guard_map, _mc, True)
+        def dummy_func():
+            pass
+
+        dummy_func()
+        self.assertFalse(self.service_running.called)
+        self.assertFalse(self.service_stop.called)
+        self.assertTrue(_mc.called)
+
+    def test_service_guard_active_with_contexts_function_object(self):
+        class MockContext(object):
+            called = False
+
+            def complete_contexts(self):
+                self.called = True
+                return ['interfacea', 'interfaceb']
+
+        _mc = MockContext()
+
+        def lmc():
+            return _mc
+
+        @utils.service_guard({'test': ['interfacea', 'interfaceb']}, lmc, True)
+        def dummy_func():
+            pass
+
+        dummy_func()
+        self.assertFalse(self.service_running.called)
+        self.assertFalse(self.service_stop.called)
+        self.assertTrue(_mc.called)
+
+    def test_service_guard_active_with_active_function_object(self):
+        class MockContext(object):
+            called = False
+
+            def complete_contexts(self):
+                self.called = True
+                return ['interfacea', 'interfaceb']
+
+        _mc = MockContext()
+
+        @utils.service_guard({'test': ['interfacea', 'interfaceb']},
+                             _mc, lambda: False)
+        def dummy_func():
+            pass
+
+        dummy_func()
+        self.assertFalse(self.service_running.called)
+        self.assertFalse(_mc.called)
+
     def helper_test_is_api_ready(self, tgt):
         fake_config = MagicMock()
         with patch('charmhelpers.contrib.openstack.utils.'