Merge ~adam-collard/maas:2.9-dont-stop-stopped-vms into maas:2.9

[Adam Collard]

Make decompose() only try and stop VMs that aren't already stopped.

Cherry-pick b527caab1c98bcbefdda9ba731b9d2c45e921fa4

[Adam Collard (adam-collard)]

self-approve backport

review: Approve

diff --git a/src/provisioningserver/drivers/pod/lxd.py b/src/provisioningserver/drivers/pod/lxd.py
index bcb3e68..57221b2 100644
--- a/src/provisioningserver/drivers/pod/lxd.py
+++ b/src/provisioningserver/drivers/pod/lxd.py
@@ -707,7 +707,8 @@ class LXDPodDriver(PodDriver):
 
         def sync_decompose(instance_name):
             machine = client.virtual_machines.get(instance_name)
-            machine.stop(force=True, wait=True)
+            if machine.status_code != 102:  # 102 - Stopped
+                machine.stop(force=True, wait=True)
             machine.delete(wait=True)
 
         yield deferToThread(sync_decompose, context["instance_name"])
diff --git a/src/provisioningserver/drivers/pod/tests/test_lxd.py b/src/provisioningserver/drivers/pod/tests/test_lxd.py
index 99f53d9..edab76d 100644
--- a/src/provisioningserver/drivers/pod/tests/test_lxd.py
+++ b/src/provisioningserver/drivers/pod/tests/test_lxd.py
@@ -1065,6 +1065,22 @@ class TestLXDPodDriver(MAASTestCase):
             ),
         )
 
+    @inlineCallbacks
+    def test_decompose_on_stopped_instance(self):
+        pod_id = factory.make_name("pod_id")
+        context = self.make_parameters_context()
+        driver = lxd_module.LXDPodDriver()
+        Client = self.patch(driver, "get_client")
+        client = Client.return_value
+        mock_machine = Mock()
+        # Simulate the case where the VM is already stopped
+        mock_machine.status_code = 102  # 102 - Stopped
+        client.virtual_machines.get.return_value = mock_machine
+        yield driver.decompose(pod_id, context)
+
+        mock_machine.stop.assert_not_called()
+        mock_machine.delete.assert_called_once_with(wait=True)
+
 
 class TestLXDGetNicDevice(MAASTestCase):
     def test_bridged(self):