Do not attempt volume swap when guest is stopped/suspended

A swap on a stopped or suspended instance will fail silently. Remove
these allowed instance states on swap_volume:

suspended, stopped, soft_deleted

Change-Id: Iff17f7cee7a56037b35d1a361a0b3279d0a885d6
Closes-Bug: #1673090

api-ref/source/os-volume-attachments.inc

@@ -137,6 +137,9 @@ Update a volume attachment
 
 Update a volume attachment.
 
+.. note:: This action only valid when the server is in ACTIVE, PAUSED and RESIZED state,
+          or a conflict(409) error will be returned.
+
 Normal response codes: 202
 
 Error response codes: badRequest(400), unauthorized(401), forbidden(403), itemNotFound(404), conflict(409)

nova/compute/api.py

@@ -3660,8 +3660,7 @@ class API(base.Base):
 
     @check_instance_lock
     @check_instance_state(vm_state=[vm_states.ACTIVE, vm_states.PAUSED,
-                                    vm_states.SUSPENDED, vm_states.STOPPED,
-                                    vm_states.RESIZED, vm_states.SOFT_DELETED])
+                                    vm_states.RESIZED])
     def swap_volume(self, context, instance, old_volume, new_volume):
         """Swap volume attached to an instance."""
         # The caller likely got the instance from volume['attachments']

nova/tests/unit/compute/test_compute_api.py

@@ -2212,6 +2212,12 @@ class _ComputeAPIUnitTestMixIn(object):
         self._test_swap_volume_for_precheck_with_exception(
             exception.InstanceInvalidState,
             instance_update={'vm_state': vm_states.BUILDING})
+        self._test_swap_volume_for_precheck_with_exception(
+            exception.InstanceInvalidState,
+            instance_update={'vm_state': vm_states.STOPPED})
+        self._test_swap_volume_for_precheck_with_exception(
+            exception.InstanceInvalidState,
+            instance_update={'vm_state': vm_states.SUSPENDED})
 
     def test_swap_volume_with_another_server_volume(self):
         # Should fail if old volume's instance_uuid is not that of the instance

releasenotes/notes/update-swap-decorator-7622a265df55feaa.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - prevent swap_volume action if the instance is in state SUSPENDED,
+    STOPPED or SOFT_DELETED. A conflict (409) will be raised now as
+    previously it used to fail silently.
+